Many phone systems don't pass an open loop (0 volts) CPC Signal (Calling Party Control) from the CO Line to the station port.
For the phone system that can't send a DTMF digit to tell the device to hang-up, the Universal CPC Generator is the answer.
Those systems usually send dial tone or a busy signal to the station port after the CO line disconnects, which keeps the Voice Mail or other device from hanging up.
The result is Voice Mail messages that have a lot of junk at the end of them, or ports that stay tied up for a long time (or until manually reset). This makes it necessary to have more ports and bigger hard drives than are really needed, to make up for the lack of a CPC Signal.
The Universal CPC Generator goes in-front of a voice mail system, automated attendant, dictation system, OPX ports or any automated telephone device that answers the phone. It listens for the tones or silence you program, and if it hears a match for the duration of what you program, it opens the line for about 800ms to tell phone equipment that's looking for an open loop CPC to hang-up.
The Universal CPC Generator will listen for one or more tones (Precise tones in the US are made up of two or four tones sent simultaneously), or silence.
Because the Universal CPC Generator listens for one or more of eight of the tones that commonly makeup Precise tones in the US, it isn't likely to false-trigger from music or voice.
The Universal CPC Generator can also listen for silence for a duration, and then open the loop for 800ms.
Whether silence or tones will work in your application is something you'll have to think about. For example, if your automated attendant never stops talking, there will never be silence.
You may be able to use the Universal CPC Generator to solve a paging problem, where a busy signal or dial tone from a station port goes over the speakers. In a paging application you may be able to trigger the CPC in as little as 250 ms of a particular tone. You can also trigger it on a couple of seconds of silence. The only way to know for sure is to give it a try, playing with the timers in the Universal CPC Generator.
The best solution for phone systems that don't have an external page port, and where a spare CO trunk isn't available, is to use the speaker leads in an electronic station set. Find an old phone, put it in the phone room, cut the speaker out and connect the speaker leads from the phone to the input of the page amp (program that phone for the page zone you want).
More technical details on Calling Party Control can be found in our CPC Technical Bulletin