Cruising Sailors Forum Archive
AC at 20 hz
In Response To: analog phone lines have a 90 volt ring signal. 
()
() When the phone is not in use, this is a constant DC signal (about 50-60 volts). When the phone rings, the signal is a 20 hertz AC signal (about 90 volts). When in use it is a modulated DC signal (between 6 and 12 volts). The phones lines even have power during a blackout in most cases.
