Bela G. Liptak (ed.), Instrument Engineers' Handbook, Fourth Edition, Volume One: Process Measurement and Analysis, CRC Press, 2003,ISBN 1420064029 page 477 /wiki/ISBN_(identifier)
Stephen Herman, Understanding Motor Controls, Nelson Education, 2012, ISBN 1133713912, pp. 163-165 /wiki/ISBN_(identifier)
Kietzman, Shannon (26 September 2022). "What is a Level Switch?". About Mechanics. Retrieved 2022-10-28. http://www.aboutmechanics.com/what-is-a-level-switch.htm
Bela G. Liptak (ed.), Instrument Engineers' Handbook, Fourth Edition, Volume One: Process Measurement and Analysis, CRC Press, 2003,ISBN 1420064029 page 477 /wiki/ISBN_(identifier)