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Community Member

Connect to overhead paging in CM4

We have managed to build an interface to an overhead paging amp using the headset port of a 7940 phone dedicated to the application. The phone is configured for DN *1, auto-answer on headset, no call forwards, busy on 1 active call.

For the physical interface, the two outside pins of the headset plug are audio-out which we patched to the 'standard phone input' of the PA amp. The PA amp detects the interface going active and keys up. Only issue is if the phone resets, someone has to activate the headset button.

Is there any way to configure an ATA-186 to do the same thing? When we tried, the ATA generated ring-out voltage on the FXS port.. very rude noise. The docs talk about configuring different tones but nothing about auto-answer.

VIP Purple

Re: Connect to overhead paging in CM4

If you have an available FXO port, you can use that to interface to the PA. You configure a route pattern that points to that FXO port. For example, you could have an 8.@ pattern. When you dial 8, you go to the overhead paging system. The next number you dial could be used to indicate a zone if your system supports that feature. We use this option with a Valcolm system and it works very well.


Community Member

Re: Connect to overhead paging in CM4

Doesn't an FXO port need to see battery (-48) to determine the circuit is available? Or does the Valcolm system provide battery?


Community Member

Re: Connect to overhead paging in CM4

The Vlacom Unit provides a loop start trunk (FXS). It provides tone and voltage to the mating fxo port on the CME router.

When you dial the paging extension you get secondary dial tone. Press the number key corresponding to the zone you want to page, and speak.

Most valcom units have a warble tone generator for night ring when a 48v ring voltage is applied to the input from an fxs port on the router.


Re: Connect to overhead paging in CM4

There are plenty of devices made for this purpose. I prefer Valcom, simply because "it works for us".

If you already have an ATA, get a Valcom V-9970 which will connect to an FXS on the Valcom, answer after 1 ring, and play a short tone. Any audio after that point is handed as line-level audio, and can be tied in to whatever you've got (amplifier, in your case) and away you go.

The V-9970 can detect battery reversal to be used as a disconnect supervision, to ensure that the trunk doesn't stay up after the IP network hangs up. This feature has been around for a couple of years now, the ATA-18x refers to it as Polarity. Set it as appropriate:

Most of the time we couple the V-9970 with a V-9964B Stacking Feedback Eliminator, which will record the page before sending it out. Since the TDM->IP conversions add a slight amount of delay, some people find overhead paging on IP Phones to be a little odd. The V-9964B eliminates this since it queues the call up before sending it out, and also cancels recording upon receipt of any DTMF tone -- great if someone misspeaks or drops the phone or whatever while recording a page.


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