This circuit was found in a 1980s US publication. It indicates when the phone is off-hook by triggering an indicator.
September 2016 - It can be purchased from Mouser Electornics the iW1818 of Dialog Semiconductor, a...
This high-power circuit from a Popular Electronics of the 80's makes use of common SCRs that admit...
Found in a 1968 EEE, this circuit accepts frequencies from 1 to 1000 Hz and control voltages from 0.1 to...