Digicom VoiceGate ATA, User Manual

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machine or voice mail, drop the call off hold, or just release a line that might
be used for dictation or announcements.
Generally speaking, if a human is using a phone line, it doesn't matter
whether the phone equipment recognizes CPC or not, since the human will
physically hang-up the phone when they're done with the call, or they'll pick
the call up off of hold when the phone system rings back after X seconds /
minutes.
CPC is normally sent as an open (0 volts DC), ranging from 250 to 500
milliseconds. When the outside party hangs-up, either on an inbound or
outbound call, the phone equipment sees this open on the line and hangs
up. Most voice mail and phone systems have a timer setting for CPC (or
Open Loop Disconnect). I generally set CPC at 500ms, unless I have a
problem. If you set it at 800ms, and the CPC open loop signal is only
500ms, the system will never see the open loop (it never gets to 800ms). If
you set it at 500ms, and the actual CPC duration is 800ms, the phone
system will recognize the CPC since there was 0 volts (an open loop) for
500ms (it won't matter if the open loop lasted another 300ms). If you
accidentally set it for 50ms you'll probably get cut-offs, especially during a
lightning storm which sometimes results in very brief blips in the loop
current. Setting this timer for 50ms means that if the phone equipment sees
an open for 1/20th of a second (not very long), it will hang up. Setting it for
500ms means it will hang-up if it sees an open of half a second or longer.
That's much more reliable.
There's often a short open (0 volts DC) on a phone line just after you go off-
hook, or just after you've finished dialing a phone number. These are
usually very short opens, like 20 to 50ms. If your phone system Open Loop
Disconnect timer is set at 50ms, you may never be able to make a call
because every call would be cut-off as soon as you went off-hook or were
finished dialing. That Open Loop Disconnect Timer is very
important!
DTMF Dual-tone multifrequency. DTMF is the system that is used in interactive
voice-response menu systems such as the menu system for accessing
voicemail messages. The DTMF system allows the user to interact with the
menu by pressing keys on a dialpad or keyboard.
FoIP Fax over Internet Protocol
FXO Foreign Exchange Office
FXS Foreign Exchange Station
IP Internet Protocol. A data-oriented protocol used for communicating data