need help electronic/relay problem phone horn

[georgebaker123]

I need to ring a phone that activates a loud ass horn. Phone has no audio ports. I'd be tapping into the 2 wires that connect from phone circuit board to the phone ring speaker.

Inside the handset, the 2 wires show .035-.045 VAC (probed with multimeter while the phone "rings") and connect to an 8 Ohm 2W speaker inside the phone. This 8 Ohm 2W speaker needs to be replaced with a very loud horn or buzzer.

-I purchased a generic 12VDC piezo horn. Need to feed it 12VDC when phone rings. That's all.

I'm stumped. Low signal relay? Some type of inline amp? I can solder a bit, and have only a very basic understanding of this stuff.

Do I look for a low signal relay? like .03VAC to 12VDC?

Thank you

 

[betwixt]

Phones work differently from one country to the next so please tell us where this is to operate first. It would also be useful to know if the phone was connected directly to an outside line (in which case you can sense the ringing voltage) or if it operates through a switchboard (PBX/PABX system).

Worst case scenario is you place a microphone near the existing ringer and the sound it picks up triggers a timer and power source to your horn. It isn't actually that difficult to do and using that method does allow you to keep your horn and its 12 supply isolated from the phone circuits. It is important that you understand that line powered phones must not be grounded, both the lines are above ground voltage and connecting to an outside power source will stop the phone operating properly and could result in a visit from the telco!

Brian.

 

[Audioguru]

On another forum a photo shows that his phone has a multi-pins DSP IC then it is probably a cell (mobile) phone.
The "0.04VAC" he measured would produce a faint 200uW into the 8 ohm speaker that will barely be heard.