Guys,
Above I was speculating whether or not my old good and trusty DECT Telephone/Answerphone would cope with my new Vodafone VoIP fibre modem/router's use of an annoying 400Hz tone to tell the human the other guy had hung up rather than the well established one second line hold current break.
Turns out it doesn't. Came home today and one of my nuisance callers had triggered my Answerphone leaving not just 15 minutes of silence but on hitting the record limit had turned the Answerphone off.
With this new setback in mind me thinks there is perhaps a sneaky little Pico project opportunity, which given the UK's move down the VoIP telephone roll-out route and old folk like me's reluctance to update kit that isn't entirely broken could have an application here. Could even be powered from the router's own USB socket.
Pico Project Outline: Feed the existing DECT phone system from the VoIP Router via a Pico and some relay contacts to the existing phone system. Get the Pico to detect the 400Hz caller hang up signal and on detecting this trigger the relay to disconnect the line for a second or so to signal caller hang up. Given the simplicity of the tone a simple limiting amplifier should be enough to feed the Pico with a tone but as a square wave making simple pulse width detection a possibility. The input should be capable of surviving the ringing voltages and this outline is only permissable when attached to fully isolating fibre modem. There could well be a market for this.
(2963)
Above I was speculating whether or not my old good and trusty DECT Telephone/Answerphone would cope with my new Vodafone VoIP fibre modem/router's use of an annoying 400Hz tone to tell the human the other guy had hung up rather than the well established one second line hold current break.
Turns out it doesn't. Came home today and one of my nuisance callers had triggered my Answerphone leaving not just 15 minutes of silence but on hitting the record limit had turned the Answerphone off.
With this new setback in mind me thinks there is perhaps a sneaky little Pico project opportunity, which given the UK's move down the VoIP telephone roll-out route and old folk like me's reluctance to update kit that isn't entirely broken could have an application here. Could even be powered from the router's own USB socket.
Pico Project Outline: Feed the existing DECT phone system from the VoIP Router via a Pico and some relay contacts to the existing phone system. Get the Pico to detect the 400Hz caller hang up signal and on detecting this trigger the relay to disconnect the line for a second or so to signal caller hang up. Given the simplicity of the tone a simple limiting amplifier should be enough to feed the Pico with a tone but as a square wave making simple pulse width detection a possibility. The input should be capable of surviving the ringing voltages and this outline is only permissable when attached to fully isolating fibre modem. There could well be a market for this.
(2963)
Statistics: Posted by RaspISteve — Tue Sep 09, 2025 1:15 am