pabx caller id bypass

I always thought it was sent immediately after the first ring. Here's supporting info:
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I was wondering if anybody knows how to bypass a PABX for caller-ID
information, so the internally connected handsets having the feature of
showing caller-ID actually show it...
Most PABX do not transfer this caller-ID information to the internal lines
Could it be done using some passive filter system ?
Or does it need optical insulation and active parts ?
Did anybody here already try to bypass it ?
Has anybody have any information on the signal level and "frequency" of
caller -ID ?
(I do know it's sent *before* the actual ringing signal, but that's about
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Most current PBX do transfer caller ID to their extensions, as long as the analog trunk interface cards are of Caller ID supporting type. Some older (Key systems) can also be upgraded to support caller ID by updating their processor card (and trunk card(s) where needed). You cannot actually bypass the processor board of the PBX to make the Caller ID ride to the extension for several reasons: #1 the phone sets should have internal feature to show Caller ID, and not just the display. Only analog phones would qualify, not the PBX feature phones. #2 the processor actually stores the Caller ID info, and then transfers it to the feature phones using its own, proprietary protocol. This protocol is pretty heavily guarded by the manufacturers (because it lets them sell more feature phones), and it is not the same as the Caller ID you'd get from the PSTN to your regular house phone. #3 it is the processor that decides which extension the call will go to, so how do you know beforehand which extension is going to receive the CallerID sequence?
If you get lucky, and you have a key system (not a PBX), and your trunk cards are supporting Caller ID, you may try to use a separate caller ID device to see if it actually gets through or, alternatively, hook the caller ID device directly to the incoming lines, especially if your extension is only picking up one line.
Good luck!
Dmitri Abaimov, RCDD
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"Dmitri(" wrote
- well, it's an analog pabx, call it an internal central passing calls from outside line to multiple internal phones - depending on who picks up first gets the call - more as one internal phone supports caller-ID - the actual switching in the pabx is done using ordinary relays (might be interesting : type pabx is Profoon CX28 see
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