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Reference.org
Bell System Practices
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<h2 id="document-organization">Document organization</h2> <p>Issuance of Bell System Practices within the Bell System started in the late 1920s, when they replaced a similar compendium, the <i>AT&T Handbook Specifications</i>. Initially, BSPs were identified by mixed alphanumeric sequence numbers designating a section and a specific document number within each section. The sections consisted of one letter and two digits, followed by a period character and a three-digit document number. The version of each document was indicated by an issue number. For example, the section designation <i>C34.175 Issue 1</i> identified a document entitled <i>Station Dials—2 and 4 Types—Maintenance</i>. </p><p>In the 1950s, the format of BSP designations was changed to a nine-digit numerical format, written in three groups of three digits. The first three digits referred to the <i>division</i>, which indicated a broad subject area, such as <i>subscriber sets</i> or the <a href="/facts/1ESS_switch/zLe0sHrF">No. 1 ESS</a>. The next three digits indicated a specific subject area, such as the specific type of equipment used within the major division subject. The final three digits indicate the serial number of the document. The content could be general descriptive information, information on wiring and connections, test procedures, or piece-part replacement and repair information. </p><p>The BSP documents were produced in primarily two formats, <a href="/facts/Letter_(paper_size)/NsRpV24a">8 1/2"x11"</a> pages for use in office environments, and in a small, portable format (4" x 6 7/8") for use by installers on the job, carried in their service trucks. Starting in the 1970s the most frequently used BSPs were bundled in convenient handbooks each covering general subject matters, such as the <i>Station Service Manual</i>. </p><p>The 9-digit format and numbering system was also used by <a href="/facts/Nortel/VYJnskS6">Nortel</a> and <a href="/facts/ITT_Corporation/X2Fhl3IS">ITT Corporation</a> due to their provenance from the Bell System's manufacturing unit, <a href="/facts/Western_Electric/j15TJJcx">Western Electric</a>. </p> <h2 id="changes-after-divestiture">Changes after divestiture</h2> <p>After the <a href="/facts/Bell_System_divestiture/W2WFN3nb">Bell System divestiture</a> of 1984, AT&T maintained the basic organization and maintenance of the publication under the revised name <i>AT&T Practices</i>, but the publication was later divided among the new companies created by divestiture. Specifically, the <i>AT&T Practices</i> covered most equipment topics that stayed with <a href="/facts/Bell_Labs/fKP5Gk0H">Bell Labs</a>, which acquired the name <i>AT&T</i>. <i>Bellcore Recommendation</i> covered network maintenance and design topics transferred to <a href="/facts/Bellcore/MBQAkk4J">Bellcore</a>. <i>Bell Service Practices</i> (and variations) referred to the plant and technical reference maintained by the various <a href="/facts/Regional_Bell_Operating_Company/9azPk76z">Regional Bell Operating Companies</a>. <i>Lucent Technology Practices</i>, and other publications contained product lines taken over by the respective manufacturers. <a href="/facts/Avaya/FcS0TJcg">Avaya</a> and <a href="/facts/Alcatel-Lucent/X0rLGYr7">Alcatel-Lucent</a> still publish practices using the 9-digit section numbering format. </p> <h2 id="bsp-nine-digit-numerical-index">BSP nine-digit numerical index</h2> <table><tbody><tr><th>Section</th><th>Reference</th><th>Description</th></tr><tr><td>GENERAL INFORMATION</td><td>000-000-000</td><td>General Information - Bell System Practices</td></tr><tr><td>GENERAL INFORMATION</td><td>000-000-001</td><td>Master Alphabetical Index - All Divisions</td></tr><tr><td>GENERAL INFORMATION</td><td>000-000-005</td><td>Master Numerical Index - All Divisions</td></tr><tr><td>GENERAL INFORMATION</td><td>000-000-006</td><td>Index of Maintenance Practices Available in Handbook Size</td></tr><tr><td>GENERAL INFORMATION</td><td>000-000-007</td><td>Master Alphabetical Index—Task Oriented Practices</td></tr><tr><td>GENERAL INFORMATION</td><td>001-000-000</td><td>(Reserved for company-issued administrative practices. The Number assignments are to be made locally.)</td></tr><tr><td>GENERAL INFORMATION</td><td>002-000-000</td><td>(Reserved for company-issued administrative practices. The Number assignments are to be made locally.)</td></tr><tr><td>GENERAL INFORMATION</td><td>003-000-000</td><td>(Reserved for company-issued administrative practices. The Number assignments are to be made locally.)</td></tr><tr><td>GENERAL INFORMATION</td><td>004-000-000</td><td>(Reserved for company-issued administrative practices. The Number assignments are to be made locally.)</td></tr><tr><td>GENERAL INFORMATION</td><td>005-000-000</td><td>Abbreviations, Definitions, Drawings, Requirement Tables, Specifications, and Symbols</td></tr><tr><td>GENERAL INFORMATION</td><td>006-000-000</td><td>Microfilm Systems</td></tr><tr><td>GENERAL INFORMATION</td><td>007-000-000</td><td>Information Systems</td></tr><tr><td>GENERAL INFORMATION</td><td>010-000-000</td><td>General Methods</td></tr><tr><td>COMMON</td><td>020-000-000</td><td>General Information- Divisions 020 to 178 Inclusive</td></tr><tr><td>APPARATUS</td><td>024-000-000</td><td>Amplifiers, Controllers, Control Units, Regulators, and Electron Tubes</td></tr><tr><td>APPARATUS</td><td>026-000-000</td><td>Banks, Clutches, Commutators and Commutator Brushes, Elevator Apparatus, Multiple Brushes and Rods, and Trip Rods for Panel Offices - Circuit Breakers, Compensators, Connectors, Control Panels, Fuses and Mountings, Magnetic Switches, Selectors, and Starters</td></tr><tr><td>APPARATUS</td><td>028-000-000</td><td>Autotransformers, Bells, Buzzers, Dials, Dial Adapters and Mountings, Gongs, Head Telephone Sets, Headsets, Potentiometers, Rheostats, Ringers, and Sounders</td></tr><tr><td>APPARATUS</td><td>030-000-000</td><td>Calculogrophs, Call Timing Switch, Cameras, Clocks, Counters, Photo Processors, Registers, Selector Multiple Designation Cards, Switches, Tape Printers, Ticketers, Timers, and Time Stamp</td></tr><tr><td>APPARATUS</td><td>032-000-000</td><td>Capacitors, Connectors, Cords, Cord Reels, Diodes, Drops, Jacks, Keys, lamps, Plugs, Resistors, Signals, Sockets, Thermistors, Transistors, and Varistors</td></tr><tr><td>APPARATUS</td><td>034-000-000</td><td>Distributors, Regenerators, and Regenerative Repeaters for Teletypewriter Service - AMA Tope Reels and Reeler, Cleaning Cabinet, Perforators, Readers, Recorders, Recorder Reproducers, Tape Announcing Machine, and Translators</td></tr><tr><td>APPARATUS</td><td>040-000-000</td><td>Relays</td></tr><tr><td>MISCELLANEOUS EQUIPMENT, MATERIALS, CIRCUITS, AND METHODS</td><td>065-000-000</td><td>Miscellaneous Equipment and Materials</td></tr><tr><td>MISCELLANEOUS EQUIPMENT, MATERIALS, CIRCUITS, AND METHODS</td><td>067-000-000</td><td>Concentrators</td></tr><tr><td>MISCELLANEOUS EQUIPMENT, MATERIALS, CIRCUITS, AND METHODS</td><td>069-000-000</td><td>Miscellaneous Methods</td></tr><tr><td>TOOLS AND GAUGES</td><td>074-000-000</td><td>Catalogue Information- Tools</td></tr><tr><td>TOOLS AND GAUGES</td><td>074-000-000</td><td>Index of Tools - Switching System and Power</td></tr><tr><td>TOOLS AND GAUGES</td><td>075-000-000</td><td>Tools and Materials (Common Usage)- Maintenance, Selection, and Use</td></tr><tr><td>TOOLS AND GAUGES</td><td>076-000-000</td><td>Tools and Materials - Switching Systems and Power - Maintenance, Selection, and Use</td></tr><tr><td>TOOLS AND GAUGES</td><td>080-000-000</td><td>Tools and Materials- Customer Equipment</td></tr><tr><td>TOOLS AND GAUGES</td><td>081-000-000</td><td>Tools and Materials - Outside Plant</td></tr><tr><td>TOOLS AND GAUGES</td><td>084-000-000</td><td>Catalogue Information - Gauges - Electrical Indicating Instruments and Meters</td></tr><tr><td>TOOLS AND GAUGES</td><td>084-000-000</td><td>Alphabetical Index - Gauges - Description</td></tr><tr><td>TOOLS AND GAUGES</td><td>085-000-000</td><td>Gouges !Common Usage! - Maintenance, Selection, and Use</td></tr><tr><td>TEST EQUIPMENT</td><td>100-000-000</td><td>Test Equipment, Electrical Indicating Instruments and Meters (Common Usage) - Maintenance, Selection, and Use</td></tr><tr><td>TEST EQUIPMENT</td><td>102-000-000</td><td>Test Equipment, Electrical Indicating Instruments and Meters !Switching Systems and Pawed - Maintenance, Selection, and Use</td></tr><tr><td>TEST EQUIPMENT</td><td>103-000-000</td><td>Transmission Test Equipment</td></tr><tr><td>TEST EQUIPMENT</td><td>104-000-000</td><td>Radio Test Equipment</td></tr><tr><td>TEST EQUIPMENT</td><td>105-000-000</td><td>PBX and Station Test Equipment</td></tr><tr><td>TEST EQUIPMENT</td><td>106-000-000</td><td>Outside Plant Electrical Test Equipment</td></tr><tr><td>TEST EQUIPMENT</td><td>107-000-000</td><td>Data and Teletypewriter Test Equipment</td></tr><tr><td>POWER</td><td>155-000-000</td><td>Alternators, Engine-Alternators, Gas Turbine Alternators, Tone Alternators, Tone Machines, Ringing and Coin Control Generators, Charging Generators and Motor-Generators</td></tr><tr><td>POWER</td><td>157-000-000</td><td>Batteries</td></tr><tr><td>POWER</td><td>159-000-000</td><td>Engines and Engine Sets, Motors, Dynamotors, and Drives</td></tr><tr><td>POWER</td><td>161-000-000</td><td>Speed Reduction Units, Converters, Inverters, Air Dryers, Compressors, Compressor Dehydrators, Dehydrators, Exhauster Sets, Fans, Tube Cooling Systems, Ventilating Equipment, Call Announcer Machines, and Waveguides</td></tr><tr><td>POWER</td><td>163-000-000</td><td>Interrupters, Ringing Machines, and Pole Changers</td></tr><tr><td>POWER</td><td>167-000-000</td><td>Power Plants, Power Units, and Power Supply</td></tr><tr><td>POWER</td><td>169-000-000</td><td>Rectifiers and Filament Supplies</td></tr><tr><td>POWER</td><td>171-000-000</td><td>Miscellaneous Power Circuits and Equipment</td></tr><tr><td>SIGNALING EQUIPMENT</td><td>179-000-000</td><td>Signaling Circuits and Associated Ringer Circuits</td></tr><tr><td>OPERATIONS SUPPORT SYSTEMS</td><td>190-000-000</td><td>Operations Centers and Support Systems - Operations, Maintenance, and Administration</td></tr><tr><td>SWITCHING SYSTEMS</td><td>201-000-000</td><td>Supplemental Information - Central Offices</td></tr><tr><td>SWITCHING SYSTEMS</td><td>201-000-005</td><td>Alphabetical Index for Division 201</td></tr><tr><td>SWITCHING SYSTEMS</td><td>205-000-000</td><td>Automatic Data Test Circuits</td></tr><tr><td>SWITCHING SYSTEMS</td><td>210-000-000</td><td>Service Observing, and Plant and Traffic Desks</td></tr><tr><td>SWITCHING SYSTEMS</td><td>211-000-000</td><td>No. 1, 3, 5, and 6 Toll Offices; No. 1, 3, 5, and 6 Toil Switchboards; and No. 6A Teletypewriter Switchboard</td></tr><tr><td>SWITCHING SYSTEMS</td><td>212-000-000</td><td>No. 4A and 4M Toil Switching Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>215-000-000</td><td>Panel Offices</td></tr><tr><td>SWITCHING SYSTEMS</td><td>216-000-000</td><td><a href="/facts/Crossbar_switch/fSDXkMzf">No. 1 Crossbar Offices</a></td></tr><tr><td>SWITCHING SYSTEMS</td><td>218-000-000</td><td>No. 3, No. 5, and No. 5A Crossbar Offices</td></tr><tr><td>SWITCHING SYSTEMS</td><td>218-000-001</td><td>Alphabetical index.- No. 5 Crossbar</td></tr><tr><td>SWITCHING SYSTEMS</td><td>218-000-002</td><td>Alphabetical Index - No. 5A Crossbar</td></tr><tr><td>SWITCHING SYSTEMS</td><td>218-000-003</td><td>Alphabetical Index - No. 3 Crossbar</td></tr><tr><td>SWITCHING SYSTEMS</td><td>218-779-000</td><td>Alphabetical Index - No. 5 Crossbar Offices - Arranged With Call Data Transmitter</td></tr><tr><td>SWITCHING SYSTEMS</td><td>218-799-000</td><td>Alphabetical Index - No. 5 Crossbar Offices - Arranged With Electronic Translation System</td></tr><tr><td>SWITCHING SYSTEMS</td><td>220-000-000</td><td>Crossbar Tandem Offices</td></tr><tr><td>SWITCHING SYSTEMS</td><td>225-000-000</td><td>Testing Information Applying to Specific Step-byStep and Community Dial Offices</td></tr><tr><td>SWITCHING SYSTEMS</td><td>226-000-000</td><td>Equipment Common to More Than One Type Step-by-Step and Community Dial Office</td></tr><tr><td>SWITCHING SYSTEMS</td><td>226-000-005</td><td>Alphabetical Index - Step-by-Step and Community Dial Offices</td></tr><tr><td>SWITCHING SYSTEMS</td><td>227-000-000</td><td>General and Testing Information Applying to Intertoll Dialing, CAMA, AMA, ANI, "TOUCH-TONE®" Calling and Common Control Equipment - Step-by-Step Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>230-000-000</td><td>Data Network Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>230-100-006</td><td>Transaction Network - Reference and Supplemental Information</td></tr><tr><td>SWITCHING SYSTEMS</td><td>231-000-000</td><td><a href="/facts/1ESS_switch/zLe0sHrF">No. 1 and No. 1A Electronic Switching Systems (ESS)</a></td></tr><tr><td>SWITCHING SYSTEMS</td><td>231-000-001</td><td>Alphabetical Index of 231 Division Section Titles—No. 1 and. No. 1A Electronic Switching Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>232-000-000</td><td>No. 2 Electronic Switching System (ESS)</td></tr><tr><td>SWITCHING SYSTEMS</td><td>233-000-000</td><td>No. 3 Electronic Switching System (ESS)</td></tr><tr><td>SWITCHING SYSTEMS</td><td>233-000-010</td><td>Interdivisional Numerical Index - Excluding Division 233 - No. 3 Electronic Switching System</td></tr><tr><td>SWITCHING SYSTEMS</td><td>234-000-000</td><td><a href="/facts/4ESS_switch/HWCjgKQ7">No. 4 Electronic Switching System (ESS)</a></td></tr><tr><td>SWITCHING SYSTEMS</td><td>234-000-005</td><td>Interdivisional Numerical Index - No. 4 Electronic Switching System</td></tr><tr><td>SWITCHING SYSTEMS</td><td>235-000-000</td><td><a href="/facts/5ESS_switch/n1xRexFM">No. 5 Electronic Switching. System (ESS)</a></td></tr><tr><td>SWITCHING SYSTEMS</td><td>240-000-000</td><td><a href="/facts/1ESS_switch/zLe0sHrF">No. 1 0 1 Electronic Switching System (ESS)</a></td></tr><tr><td>SWITCHING SYSTEMS</td><td>241-000-000</td><td>General Trade Switching Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>250-000-000</td><td><a href="/facts/Traffic_Service_Position_System/uLj3ntmw">Traffic Service Systems</a></td></tr><tr><td>SWITCHING SYSTEMS</td><td>252-000-000</td><td>Traffic Management Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>254-000-000</td><td>Stored Program Control</td></tr><tr><td>SWITCHING SYSTEMS</td><td>255-000-000</td><td>Processor Controlled Ancillary Systems</td></tr><tr><td>SWITCHING SYSTEMS</td><td>250-000-010</td><td>Interdivisional Numerical Index - No. 1 A Voice Storage System</td></tr><tr><td>SWITCHING SYSTEMS</td><td>256-000-000</td><td>Common Channel Signaling System (CCSS)</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>300-000-000</td><td>Transmission Systems and Testing - Cross Reference lists</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>301-000-000</td><td>Transmission Performance Measurement Plans</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>302-000-000</td><td>Transmission Test Line Directories</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>304-000-000</td><td>Transmission Data</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>309-000-000</td><td>Switched Services Networks</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>310-000-000</td><td>Nonswitched Special Services System</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>311-000-000</td><td>Switched Special Services Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>312-000-000</td><td>Private Line Data Systems and Services</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>314-000-000</td><td>Digital and Analogue Data Transmission Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>318-000-000</td><td>Television Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>320-000-000</td><td>Program Transmission Systems and Services</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>330-000-000</td><td>Cable and Open-Wire Testing and Trouble location Methods</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>331-000-000</td><td>Transmission Noise Testing, Central Office PBX Customer lines and Equipment</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>332-000-000</td><td>Voice-frequency Telephone Repeaters, Pilot Wire Regulators, Echo Suppressors, Composite Sets and Associated Equipment</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>333-000-000</td><td>Interoffice Signaling Systems and Testing</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>340-000-000</td><td><a href="/facts/Videophone/Ya9TMFQD">PICTUREPHONE®</a> Services - Baseband Video Transmission</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>341-000-000</td><td><a href="/facts/Videophone/Ya9TMFQD">PICTUREPHONE®</a> Transmission - Performance Plan</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>354-000-000</td><td>Frequency Generating Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>355-000-000</td><td>Type K Carrier Telephone Systems and Associated Equipment Components</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>356-000-000</td><td>Analog Multiplex Terminal Equipment</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>357-000-000</td><td>Wire-Line Entrance Links and Broadband Entrance Links and Interconnection</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>358-000-000</td><td>Type L1 Carrier Telephone System and Associated Equipment Components</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>359-000-000</td><td>L3, L4, L4S, L5, and LSE Carrier</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>360-000-000</td><td>Maintenance Center Tests - Equipment Components- Type L1 and L3 Carrier Telephone Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>361-000-000</td><td>Service Center Tests - type N, 0, and ON Carrier Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>362-000-000</td><td>Type N, 0, and ON Carrier Telephone Systems and Associated Equipment Components</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>363-000-000</td><td>Pair Gain Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>364-000-000</td><td>Submarine Cable Systems !long lines Only!</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>365-000-000</td><td>Digital Transmission Systems</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>370-000-000</td><td>TA SI (long Lines Only)</td></tr><tr><td>TRANSMISSION AND SIGNALING SYSTEMS AND TESTING</td><td>371-000-000</td><td>Broadband Restoration</td></tr><tr><td>RADIO</td><td>400-000-000</td><td>Radio Administration</td></tr><tr><td>RADIO</td><td>402-000-000</td><td>Antennas, Transmission lines, and Waveguide</td></tr><tr><td>RADIO</td><td>403-000-000</td><td>Coastal Harbor, High Seas, Overseas, and Emergency Point-to-Point Radio</td></tr><tr><td>RADIO</td><td>404-000-000</td><td>Manual Mobile Radio</td></tr><tr><td>RADIO</td><td>405-000-000</td><td>NJ, MKS, and ML Mobile Radiotelephone</td></tr><tr><td>RADIO</td><td>406-000-000</td><td>Air-Ground Radio</td></tr><tr><td>RADIO</td><td>407-000-000</td><td>Personal Radio Services</td></tr><tr><td>RADIO</td><td>408-000-000</td><td>Motorola, RCA, Federal, REL, Narrow band Auxiliary Channel and Other Non-Western Electric Microwave Radio, and TV Off-the-Air Pick-Up Services</td></tr><tr><td>RADIO</td><td>409-000-000</td><td>TE, DT, Tl, and TM Microwave Radio</td></tr><tr><td>RADIO</td><td>410-000-000</td><td>TD-2 Microwave Radio</td></tr><tr><td>RADIO</td><td>411-000-000</td><td>TD-3 Microwave Radio</td></tr><tr><td>RADIO</td><td>412-000-000</td><td>TH-1 Microwave Radio</td></tr><tr><td>RADIO</td><td>413-000-000</td><td>TH-3 Microwave Radio</td></tr><tr><td>RADIO</td><td>415-000-000</td><td>TD-3 Microwave Radio</td></tr><tr><td>RADIO</td><td>416-000-000</td><td>TN-1 Microwave Radio</td></tr><tr><td>RADIO</td><td>417-000-000</td><td>3A-Radio Digital Systems</td></tr><tr><td>RADIO</td><td>419-000-000</td><td>Single Sideband Microwave Radio Systems</td></tr><tr><td>RADIO</td><td>420-000-000</td><td>Microwave Radio - Common Equipment</td></tr><tr><td>RADIO</td><td>421-000-000</td><td>FR/DR Microwave Radio System</td></tr><tr><td>RADIO</td><td>422-000-000</td><td>Common Microwave Radio- Transmission Systems</td></tr><tr><td>CUSTOMER EQUIPMENT</td><td>460-000-000</td><td>General Information</td></tr><tr><td>CUSTOMER EQUIPMENT</td><td>460-000-006</td><td>Alphabetic-Numeric Index - Station, Key, PBX, and Private Service Systems</td></tr><tr><td>CUSTOMER EQUIPMENT</td><td>461-000-000</td><td>Wiring and Cabling</td></tr><tr><td>CUSTOMER EQUIPMENT</td><td>462-000-000</td><td>Drop and Block Wiring and Dedicated Plant</td></tr><tr><td>CUSTOMER EQUIPMENT</td><td>463-000-000</td><td>Miscellaneous Station Apparatus for Use With Station Installations</td></tr><tr><td>SPECIAL SERVICES</td><td>471-000-000</td><td>Other Common Carriers</td></tr><tr><td>SPECIAL SERVICES</td><td>473-000-000</td><td>Intro-PBX Protection of Service, Code Calling, Customer Training, Dispatching, Emergency Reporting, Interface Trunks, Message Waiting, Recorded Telephone Dictation, Telephone Answering Systems, and Transmitter Transfer</td></tr><tr><td>SPECIAL SERVICES</td><td>475-000-000</td><td>Call Distributing System No. IS, Information Desks, and Order Turrets</td></tr><tr><td>SPECIAL SERVICES</td><td>476-000-000</td><td>Force Administration Data System (FADS)- Automatic Call Distributing System (ACD), No. 2A, 28, and 3A and Call Distributing System No. 4A</td></tr><tr><td>SPECIAL SERVICES</td><td>480-000-000</td><td>Private Service Systems</td></tr><tr><td>SPECIAL SERVICES</td><td>481-000-000</td><td>Teleconferencing Service</td></tr><tr><td>STATION EQUIPMENT</td><td>500-000-000</td><td>General Considerations for Station Installations</td></tr><tr><td>STATION EQUIPMENT</td><td>501-000-000</td><td>Station Set Components</td></tr><tr><td>STATION EQUIPMENT</td><td>502-000-000</td><td>Common Battery Station Sets</td></tr><tr><td>STATION EQUIPMENT</td><td>503-000-000</td><td>Modular Station Sets - Common Battery</td></tr><tr><td>STATION EQUIPMENT</td><td>504-000-000</td><td>Selector Consoles, Telephone Consoles, and Apparatus Units</td></tr><tr><td>STATION EQUIPMENT</td><td>506-000-000</td><td>Public telephone Sets</td></tr><tr><td>STATION EQUIPMENT</td><td>508-000-000</td><td>Public Telephone Enclosures and Miscellaneous Accessories</td></tr><tr><td>STATION EQUIPMENT</td><td>510-000-000</td><td>Station Sets and Coin Collectors—local Battery and Magneto</td></tr><tr><td>STATION EQUIPMENT</td><td>512-000-000</td><td>Automatic Dialers, Station Keys, Key Equipment, Interphone Systems, Modular Units, and Speakerphone Systems</td></tr><tr><td>STATION EQUIPMENT</td><td>514-000-000</td><td>Telephone Answering and Announcement Sets and Systems</td></tr><tr><td>STATION EQUIPMENT</td><td>518-000-000</td><td>Key Telephone Systems, Video Telephone Stations, and Switching Systems</td></tr><tr><td>STATION EQUIPMENT</td><td>518-451-110</td><td>HORIZON® Communications System - Feature Document Cross-Reference Guide</td></tr><tr><td>STATION EQUIPMENT</td><td>529-000-000</td><td>Station Apparatus and Equipment Intended Solely for Specially-..engineered lines - Not for General Telephone Use</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>533-000-000</td><td>Customer Premises Systems (ESS Provided Customer Services)</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>533-000-001</td><td>Interdivisional Alphanumeric Indexes - ESS Provided Services -Customer Premises Systems</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>534-000-000</td><td>Sections Applying to More Than One PBX Series - 500, 600, 700, and 800 Series- Manual and Dial PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>536-000-000</td><td>500 Series PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>538-000-000</td><td>600 Series PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>540-000-000</td><td>Sections Applying to More Than One 700 Series PBX Including Centrex CU, Attendant Equipment for Centrex CO, and "TOUCH-TONE®" Calling</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>541-000-000</td><td>700C and 710C PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>542-000-000</td><td>701- and 711-Type PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>543-000-000</td><td>702A PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>546-000-000</td><td>740-Type PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>548-000-000</td><td>750A PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>550-000-000</td><td>755A PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>551-000-000</td><td>756A, 757A, 758A, 758B, 758C, 761, and 770 PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>553-000-000</td><td>800 Series PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>554-000-000</td><td>"DIMENSION®" PBX</td></tr><tr><td>PRIVATE BRANCH EXCHANGES</td><td>554-191-100</td><td>"DIMENSION®" PBX- Feature Document Reference Guide</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>570-000-000</td><td>Teletypewriter General Information - Miscellaneous Apparatus and Auxiliary' Equipment</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>570-000-003</td><td>Master Cross-Reference Index of Port Numbers and Associated 9-digit Sections</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>572-000-000</td><td>14- 15-, 19-, and 20-Type Teletypewriters</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>573-000-000</td><td>28- Type Teletypewriters</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>574-000-000</td><td>Teletypewriter 30 Series and Teleprinters</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>578-000-000</td><td>Miscellaneous Data Terminals</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>579-000-000</td><td>Teletypewriter Field Maintenance Practices/Field Installation Maintenance Practices</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>580-000-000</td><td>Teletypewriter Switching Systems</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>581-000-000</td><td>Teletypewriter Selective Calling Systems</td></tr><tr><td>TELETYPEWRITER AND OTHER DATA TERMINALS</td><td>582-000-000</td><td>DATASPEED® Services- Systems, Services and Components</td></tr><tr><td>DATA SYSTEMS</td><td>590-000-000</td><td>General Information</td></tr><tr><td>DATA SYSTEMS</td><td>591-000-000</td><td>1 00 Series Data Sets and Associated Services</td></tr><tr><td>DATA SYSTEMS</td><td>592-000-000</td><td>200 Series Data Sets and Associated Services</td></tr><tr><td>DATA SYSTEMS</td><td>593-000-000</td><td>300 Series Data Sets and Associated Services</td></tr><tr><td>DATA SYSTEMS</td><td>594-000-000</td><td>400 Series Data Sets and Associated Services</td></tr><tr><td>DATA SYSTEMS</td><td>595-000-000</td><td>500-Type Service Units and Sets for Digital Systems/Services</td></tr><tr><td>DATA SYSTEMS</td><td>596-000-000</td><td>600 Series Data Sets and Associated Services</td></tr><tr><td>DATA SYSTEMS</td><td>598-000-000</td><td>800 Series Auxiliary Equipments</td></tr><tr><td>OUTSIDE PLANT</td><td>620-000-000</td><td>General</td></tr><tr><td>OUTSIDE PLANT</td><td>620-000-005</td><td>Outside Plant - Construction and Maintenance - Permuted Alphabetical Index</td></tr><tr><td>OUTSIDE PLANT</td><td>621-000-000</td><td>Pole Lines</td></tr><tr><td>OUTSIDE PLANT</td><td>622-000-000</td><td>Conduit, Manholes, and Cable Ducts</td></tr><tr><td>OUTSIDE PLANT</td><td>623-000-000</td><td>Open Wire</td></tr><tr><td>OUTSIDE PLANT</td><td>624-000-000</td><td>Multiple Wire</td></tr><tr><td>OUTSIDE PLANT</td><td>626-000-000</td><td>Cables, Wire, and Apparatus - General</td></tr><tr><td>OUTSIDE PLANT</td><td>627-000-000</td><td>Aerial, Block, and House Cable</td></tr><tr><td>OUTSIDE PLANT</td><td>628-000-000</td><td>Underground Cable</td></tr><tr><td>OUTSIDE PLANT</td><td>629-000-000</td><td>Buried Plant</td></tr><tr><td>OUTSIDE PLANT</td><td>630-000-000</td><td>Submarine Cable</td></tr><tr><td>OUTSIDE PLANT</td><td>631-000-000</td><td>Cable Terminals</td></tr><tr><td>OUTSIDE PLANT</td><td>632-000-000</td><td>Cable Splicing</td></tr><tr><td>OUTSIDE PLANT</td><td>633-000-000</td><td>Splice Closures</td></tr><tr><td>OUTSIDE PLANT</td><td>634-000-000</td><td>Electrical Cable Testing and Identification</td></tr><tr><td>OUTSIDE PLANT</td><td>635-000-000</td><td>Electrolysis - Outside Plant</td></tr><tr><td>OUTSIDE PLANT</td><td>636-000-000</td><td>Main Frame Terminations and Connectors</td></tr><tr><td>OUTSIDE PLANT</td><td>637-000-000</td><td>Cable Pressure Systems</td></tr><tr><td>OUTSIDE PLANT</td><td>637-600-011</td><td>Expanded Cable Pressure Monitoring System (CMPS)</td></tr><tr><td>OUTSIDE PLANT</td><td>638-000-000</td><td>Electrical Protection and Bonding</td></tr><tr><td>OUTSIDE PLANT</td><td>639-000-000</td><td>Concentrators - Outside Plant</td></tr><tr><td>OUTSIDE PLANT</td><td>640-000-000</td><td>Outside Plant - Carrier Apparatus</td></tr><tr><td>OUTSIDE PLANT</td><td>643-000-000</td><td>Coil and Capacitor Cases and Apparatus Cases for Inductors and Filters</td></tr><tr><td>OUTSIDE PLANT</td><td>644-000-000</td><td>Upkeep</td></tr><tr><td>OUTSIDE PLANT</td><td>649-000-000</td><td>Construction Equipment - Outside Plant (also see Divisions 010, 075, 081, 106, and 157)</td></tr><tr><td>TEST CENTER OPERATION</td><td>660-000-000</td><td>Test Center Operation</td></tr><tr><td>TEST CENTER OPERATION</td><td>660-000-005</td><td>Alphabetical Index- Test Center Operation (Divisions 660 Through 669)</td></tr><tr><td>TEST CENTER OPERATION</td><td>660-168-010</td><td>Automated Repair Service Bureau - Documentation Index</td></tr><tr><td>TEST CENTER OPERATION</td><td>662-000-000</td><td>Cable and Local Test Desks and Local Test Cabinets</td></tr><tr><td>TEST CENTER OPERATION</td><td>664-000-000</td><td>Test boards for Other Than Special Services</td></tr><tr><td>TEST CENTER OPERATION</td><td>666-000-000</td><td>Testboords and Test Positions for Special Services</td></tr><tr><td>TEST CENTER OPERATION</td><td>667-000-000</td><td>Switched Maintenance Access Systems (SMAS)</td></tr><tr><td>TEST CENTER OPERATION</td><td>668-000-000</td><td>Data Test Centers</td></tr><tr><td>LOOP ASSIGNMENT</td><td>680-000-000</td><td>Loop Assignment - Distribution Service</td></tr><tr><td>LOOP ASSIGNMENT</td><td>680-000-005</td><td>Alphabetical Index - Plant Assignment - Divisions 680 through 689</td></tr><tr><td>LOOP ASSIGNMENT</td><td>680-400-010</td><td>Index - Telephone Set field Inventory Control</td></tr><tr><td>LOOP ASSIGNMENT</td><td>682-000-000</td><td>Trunk Plant and Special Services</td></tr><tr><td>MOTOR VEHICLES</td><td>720-000-000</td><td>Motor Vehicles and Construction Apparatus</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>740-000-000</td><td>General Information</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>740-000-001</td><td>Overall Supplies - Divisions · 740 through 749</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>740-000-002</td><td>Materials Management Operations Safety Procedure References</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>741-000-000</td><td>Supporting Functions</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>742-000-000</td><td>Supply Controls</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>743-000-000</td><td>Supply Ordering and Computer Controls</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>744-000-000</td><td>Supply Distribution</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>745-000-000</td><td>Material Returns</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>746-000-000</td><td>Supply Functions - Miscellaneous</td></tr><tr><td>MATERIALS MANAGEMENT</td><td>747-000-000</td><td>Plug-In Equipment- Central Office and Customer Premises Switching</td></tr><tr><td>BUSINESS INFORMATION SYSTEMS</td><td>750-000-000</td><td>BISP General</td></tr><tr><td>BUSINESS INFORMATION SYSTEMS</td><td>751-000-000</td><td>Common language</td></tr><tr><td>BUSINESS INFORMATION SYSTEMS</td><td>756-000-000</td><td>Trunks and Special Services</td></tr><tr><td>BUILDINGS</td><td>760-000-000</td><td>Building Engineering</td></tr><tr><td>BUILDINGS</td><td>760-000-005</td><td>Alphabetical Index- Divisions 760 and 770- Building Engineering and Building Operation</td></tr><tr><td>BUILDINGS</td><td>770-000-000</td><td>Building Operation</td></tr><tr><td>ENGINEERING PLANNING</td><td>780-000-000</td><td>Network Operations Methods</td></tr><tr><td>ENGINEERING PLANNING</td><td>780-000-010</td><td>Interdivisional Numerical Index - Network Administration Technical Planning</td></tr><tr><td>ENGINEERING PLANNING</td><td>788-000-000</td><td>Business Services Planning and Operations</td></tr><tr><td>ENGINEERING PLANNING</td><td>788-100-000</td><td>Cross-Reference Index- Business Services Facilities Engineering Practices (BSFEP) to Bell System Practices</td></tr><tr><td>ENGINEERING PLANNING</td><td>788-100-101</td><td>Recommended Document list - Business Service Traffic Engineering</td></tr><tr><td>ENGINEERING PLANNING</td><td>788-102-100</td><td>Cross-Reference Index- Business Services Facilities Administrative Practices (BSFAP) to Bell System Practices</td></tr><tr><td>ENGINEERING PLANNING</td><td>788-102-101</td><td>Recommended Document List - Business Services Traffic Administration</td></tr><tr><td>ENGINEERING ADMINISTRATION</td><td>790-000-000</td><td>Engineering Administrative Practices</td></tr><tr><td>COMMON LANGUAGE</td><td>795-000-000</td><td>Common language</td></tr><tr><td>COMMON LANGUAGE</td><td>795-200-006</td><td>Alphabetical Index of Basic, Codes—Common language Equipment Identification (CLE)</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>800-000-000</td><td>Cross-Reference lists, Administrative Information, General Equipment Requirements for Installation and Manufacturing, and General Performance Requirements</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>801-000-000</td><td>Common Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>802-000-000</td><td>Power Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>804-000-000</td><td>Toil Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>806-000-000</td><td>Radio Systems and Television Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>807-000-000</td><td>Data Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>809-000-000</td><td>Private Branch Exchange Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>811-000-000</td><td>Private Service Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>812-000-000</td><td>Station Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>814-000-000</td><td>Step-by-Step Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>815-000-000</td><td>Panel Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>816-000-000</td><td>No, I Crossbar System</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>817-000-000</td><td>Tandem Crossbar System</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>818-000-000</td><td>No. 4 Type Toil Switching System</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>819-000-000</td><td>No. 3, No. 5, and No. SA Crossbar Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>820-000-000</td><td>No. 1, 1A, 2, 2A, 3 and 4 Electronic Switching Systems and No. 1A Processor</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>821-000-000</td><td>Traffic Service Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>822-000-000</td><td>Traffic Management Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>823-000-000</td><td>No. 101 Electronic Switching System</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>824-000-000</td><td>Operations Support Systems</td></tr><tr><td>EQUIPMENT DESIGN AND GENERAL REQUIREMENTS</td><td>825-000-000</td><td>Common Channel Signaling System (CCSS)</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>851-000-000</td><td>Special Services Systems - Engineering Design Information</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>852-000-000</td><td>Exchange Area and Operator Services Transmission</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>853-000-000</td><td>Toil Transmission</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>855-000-000</td><td>Carrier Engineering</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>856-000-000</td><td>Mechanized Transmission Engineering Tools</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>857-000-000</td><td>Program and Television Engineering</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>859-000-000</td><td>Signal Transmission - Engineering Considerations</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>860-000-000</td><td>PICTUREPHONE® Service Transmission Engineering</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>865-000-000</td><td>Transmission Maintenance Systems Engineering</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>870-000-000</td><td>Noise Engineering</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>873-000-000</td><td>Inductive Coordination</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>874-000-000</td><td>Supply Systems Data</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>876-000-000</td><td>Protection Practices</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>877-000-000</td><td>Corrosion Practices</td></tr><tr><td>TRANSMISSION ENGINEERING</td><td>880-000-000</td><td>Data Communications Engineering</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>900-000-000</td><td>General Information</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>900-000-100</td><td>Permuted Index - Outside Plant Engineering</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>901-000-000</td><td>Facility Planning - Study Methods and Tools</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>902-000-000</td><td>Facility Planning - Applied Transmission</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>915-000-000</td><td>Facility Design - Systems</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>916-000-000</td><td>Facility Design - Feeder Facilities</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>917-000-000</td><td>Facility Design - Distribution Facilities</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>918-000-000</td><td>Facility Design - Applied Protection</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>919-000-000</td><td>Facility Design - Structure</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>920-000-000</td><td>Facility Design - Trunk Facilities</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>928-000-000</td><td>Facility Support - Engineering Support Functions</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>929-000-000</td><td>Outside Plant Facility Support - Plant Operating Support functions</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>930-000-000</td><td>Facility Support - Maintenance and Upkeep</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>935-000-000</td><td>Management Organizing</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>936-000-000</td><td>Management Controlling</td></tr><tr><td>OUTSIDE PLANT ENGINEERING</td><td>937-000-000</td><td>Management Coordinating</td></tr><tr><td>RADIO ENGINEERING</td><td>940-000-000</td><td>Radio Engineering</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>951-000-000</td><td>Equipment Common to More Than One Type of System</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>953-000-000</td><td>Switchboard, Desks, and Associated Equipment</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>955-000-000</td><td>Step-by-Step and Community Dial Offices</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>957-000-000</td><td>No. 1 Crossbar Offices</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>958-000-000</td><td>No. 5 Crossbar Offices</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>966-000-000</td><td>Electronic Switching Systems (ESS)</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>970-000-000</td><td>Transmission Systems</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>972-000-000</td><td>Teletypewriter and Data Systems (Information Obsolete)</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>975-000-000</td><td>Signaling Systems</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>981-000-000</td><td>Equipment on Customers' Premises Special Services and Private Branch Exchanges!</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>982-000-000</td><td>Private Service Systems</td></tr><tr><td>GENERAL DESCRIPTIVE INFORMATION</td><td>984-000-000</td><td>Traffic Service and Traffic Management Systems</td></tr></tbody></table> <h2 id="external-links">External links</h2> <ul><li><a href="https://www.telecomarchive.com/plant-index.html">"Bell System Practices archive"</a>. telecomarchive.com.</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>A.B. Covey, The Bell System's Best Sellers, Bell Telephone Magazine, Summer 1952, Pages 87—95 (AT&T) <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> </ol>