DREUBEN@eagle.wesleyan.edu (Douglas Scott Reuben) (11/04/90)
Hi-
I'm wondering if anyone here knows exactly (or not so exactly :-) )
what the "wink", or I believe it is sometimes called "CPC" signal is.
I'm referring to the process by which the Central Office switch can
signal a end-user device (an answering machine, for example) that the
calling party has hung up. IE, someone calls my machine, hears the
outgoing message, thinks it is really too long, and just hangs up. The
machine "knows" that the caller has hung up even before it starts
"listening" on the line to see if anyone is recording a message or
not.
I've heard from some sources that this is done with polarity reversal,
and from others that there is just a drop in line current for a brief
momment. Is either (or both?) correct?
If anyone knows the exact timing (ie, the wink = xxx miliseconds,
etc.) and what voltages are involved, I'd really appreciate hearing
about it. Or, if you'd prefer that I not be so lazy and research it on
my own ( :-) ), could you perhaps steer to the proper sources?? I've
looked in the "Red" Radio Shack book and in my other sources, and have
found nothing dealing with this topic. So just about any info would be
helpful!
Thanks in advance for any/all help!
Doug
dreuben@eagle.wesleyan.edu
dreuben@wesleyan.bitnet
P.S. Gilbert- ( at Rochelle Com. in Texas) - I've lost my entire mail file
and could use your address again. Could you please e-mail me at the
above address? Thanks...grayt@uunet.uu.net (Tom Gray) (11/07/90)
In article <14261@accuvax.nwu.edu> DREUBEN@eagle.wesleyan.edu (Douglas Scott Reuben) writes: >I'm wondering if anyone here knows exactly (or not so exactly :-) ) >what the "wink", or I believe it is sometimes called "CPC" signal is. >I'm referring to the process by which the Central Office switch can >signal a end-user device (an answering machine, for example) that the >calling party has hung up. i.e., someone calls my machine, hears the >outgoing message, thinks it is really too long, and just hangs up. The >machine "knows" that the caller has hung up even before it starts >"listening" on the line to see if anyone is recording a message or >not. >I've heard from some sources that this is done with polarity reversal, >and from others that there is just a drop in line current for a brief >moment. Is either (or both?) correct? The problem described here occurs on loop start lines on which no answer supervision is provided. A call is answerd by a machine The answering machine needs an indication that the far end has disconnected. In the absence of answer supervision, how is this done? Normally for non-answer supervision loops a service can be provided in which the impedance of the loop is raised above 15K ohms for a short period of time. This has the effect of lowering the loop current below the off hook threshhold. Answering equipment can be designed to detect the absence of loop current on a disconnect signal. The usual means of providing this service is to open the tip (A lead for non North Americans) with a relay. in effect, the CO is providing the disconnect signal normally provided on a ground start trunk on a loop start service. Naturally if answer supervision is provided on a loop. Far end disconnect is indicated by an on hook signal. This is the reversal of battery mentioned above (assuming that reverse battery signalling is used). The service described above (called Cut Off on Disconnect around here) is the removal of loop current for a few hundred milliseconds. The exact timimgs of this cut off will vary greatly depending on the type of equipment installed.
yazz@prodnet.la.locus.com (Bob Yasi) (11/12/90)
> The service described above (called Cut Off on Disconnect around here) > is the removal of loop current for a few hundred milliseconds. The > exact timimgs of this cut off will vary greatly depending on the type > of equipment installed. My local central office has a DMS (100 or 200?) switch. The normal duration of the disconnect signal (called CPC around here) is 800 ms, or 0.8 seconds. This "signal" is the electrical equivalent of unplugging your phone for the specified duration. You can actually see it happening if you have a phone that lights up with led's using the power supplied by the phone line -- the led's turn off from the lack of power, then come back on again. But, some answering machines or other "customer provided" equipment does better with a longer signal. If you have the same switch as I do (and maybe even if you don't) you can call repair and they will set a software option for your telephone line and up the duration to 1200 ms, or 1.2 seconds. The service reps seemed to know about this as a general response to "My answering machine acts funny". In one of the conversations I had with an actual technical person in the CO, I asked if there were any other "software options" that were free. I was told there were none. Bob Yazz -- yazz@locus.com
grayt@uunet.uu.net (Tom Gray) (11/12/90)
>>I'm wondering if anyone here knows exactly (or not so exactly :-) ) >>what the "wink", or I believe it is sometimes called "CPC" signal is. Tom Gray wrote: >The problem described here occurs on loop start lines on which no >answer supervision is provided. A call is answerd by a machine The Tom Gray now humbly writes perhaps I should truly read the question before I pontificate on telephone loop siganlling. The writer asked a simple question on how his answering machine worked. I replied with the mechanisms which would be used by expensive CPE equipment which needs to eliminate fraud and to maximize the use of trunks. My answer was true for CPE. For the question on answering machines, the machine detects the end of the conversation by detecting dial tone. When the calling party clears, the connection will be broken. The local office will time out and regard the off hook from the answering machine as an origination and provide dial tone.
forrette@cory.berkeley.edu (Steve Forrette) (11/13/90)
In article <14617@accuvax.nwu.edu> you write: >For the question on answering machines, the machine >detects the end of the conversation by detecting dial tone. When the >calling party clears, the connection will be broken. The local office >will time out and regard the off hook from the answering machine as an >origination and provide dial tone. This is not true for all machines. My Panasonic DOES deal with CPC. It's really nice not having to listen to dialtone at the end of each message. Also, it can even detect a hangup during the play of the outgoing message. It stops play immediately, and resets for the next call. I've the KX-T1427 model, and it's great! (Yea, I know, if I was REALLY hi-tech, I'd have a voice board, but oh well.)