2-4 wire converters / hybrids (2009)
Elliott Sound Products AN-010 2-4 Wire Converters / Hybrids Rod Elliott (ESP) The analogue telephone system is commonly known as the PSTN - public switched telephone network, but is also called POTS - plain old telephone system. It is characterised by the operating voltage of 48V DC supplied from the exchange when the phone is 'on-hook' (not connected to the local exchange), and around 5-12V when 'off-hook' (during a call). It's a 2-wire system, with simultaneous bidirectional communication. D