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Re: [hylafax-users] Eicon Diva Server ignores RingsBeforeAnswer in config file
On Thursday 13 Dec 2007, Dan Bonelli wrote:
> The rings I was attempting to count were audible rings that I expected to
> hear when I dialed it with my cellphone, not the entries in the log files.
> /var/log/messages is saying that there are two rings, but I hear dead
> silence for a second or two, then the fax squeal, when I call. When the
> log says 'RING' twice, I'm assuming that there should be an annoying
> ringing sound made somewhere, right? My (admittedly uninformed) theory is
> that the lack of an audible ring is what's causing the remote machine to
> hang up, because the remote machine comes back with a report that says our
> line is busy, even though I can see them connect in the log files.
In the bad old days of Strowger exchanges, a circuit was established between
the two ends as soon as the last digit was dialled; and the tone in the
caller's handset was caused by the actual ringing signal (about 90V / 25Hz)
being applied to the unanswered phone at the far end. Nowadays, this is no
longer the case.
Nowadays, there is *no* circuit between the two phones. The caller is
connected to an A-D and D-A converter and the answerer is connected to a
similar arrangement. A B-channel (of which there are 30 in a single Primary
rate connection) carries bits representing audio back and forth, while a
separate channel called the D-channel is used to pass back and forth
housekeeping and status information.
The "ringing tone" you hear in your handset is generated by your own local
exchange in response to status messages coming via the D-channel from the
other party's local exchange. It is *not* necessarily in sympathy with the
actual pulses of ringing voltage applied to the called party's telephone.
However, in the case of landline-to-landline calls between exchanges belonging
to the same telephone company, the timing is usually close enough. So the
old "three rings" signal still mostly works. (Though now we have CLID, you
can be sure someone arrived home safely, or whether they are at the bus or
railway station, just from the number showing on the LCD.)
(insert figure one before at sign if replying off-list)
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