PCM30

PCM30 describes an application of <a href="/facts/Pulse-code_modulation/5gdfjtH3">pulse-code modulation</a> (PCM) in which 30 telephony <a href="/facts/Analog_signal/xDbb4uB5">analog signals</a> are binary coded into a digital signal stream. 
The term is used today mostly as a synonym for the encoding of 30 channels each with a signalling rate of 64-kbit/s. This rate is also used in the first stage of European PDH technique, so PCM30 is also known as E1. Originally it described a device in communications technology that converted the 30 analog telephone signals into a digital <a href="/facts/Bitstream/Pf9oGYyY">bit stream</a> of 2048 kbit/s.
The <a href="/facts/Pulse-code_modulation/5gdfjtH3">pulse-code modulation</a> (PCM) technology was patented and developed in France in 1938, but could not be used because suitable technology was not available until World War II. This came about with the arrival of digital systems in the 1960s when improving the performance of communications networks became a real possibility. However, this technology was not completely adopted
until the mid-1970s, due to the large amount of analog systems already in place and the high cost of digital systems, as semiconductors were very expensive. PCM's initial goal was to convert an analog voice telephone channel into a digital one based on the sampling theorem.

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PCM30