Dataplex DPX-213, User Manual

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INSTALLATION
Section 2
2-6
Copyright (C) Dataplex Pty Ltd
2.8 Closing a Connection
There are several ways to abort a call. If the call has been answered by a modem and both
are on-line, typing any key will now send that character to the attached modem. Aborting
the call in this case must be done from the on-line interactive state which is entered by
typing the escape sequence of 'pause'
+++
'pause' followed by
athK
.
The abort timer (S-Register 7) will also abort the call if the originating modem has not
established a call before S7 times out. This is normally 45 seconds but can be between 1
and 255 seconds.
Basically, a call can be terminated in several ways :
•
Hitting any key on the terminal;
•
Detection of busy tone by the DPX-213;
•
Time-out of the modem (S-Register 7);
•
Loss of carrier;
•
Typing the escape sequence ('pause'
+++
'pause') then
ath0K
.
Additionally, a call will be terminated when either Busy tone (engaged) is detected or loss
of power is applied to the modem by switching off or removing the power cord.
NOTE: If data is present, then one of the Dumb modes should be used (AT*D2).
2.9 Call Establishment Sequence
The modem placing the call is termed the originating modem and the modem at the other
end is termed the answering modem. When instructed to place a call, the originating
modem will go off-hook and the OH LED will illuminate. Typically, the originating
modem listens briefly for dial tone before dialling, places the call, and then listens for
answer tone from the answering modem. If no tone is received within a preset time (stored
in S-Register 7), the call is aborted.
The originating modem is usually silent during this initial call set-up phase, but a calling
tone can be enabled (via the AT*G command) which transmits an interrupted tone so the
called party can distinguish a data call from a voice call and activate the modem if
required.
At the answering end, the modem detects the incoming ring, counts up to the preset
number of rings (stored in S-Register 0) and then goes off-hook. It transmits an answer
tone to the calling modem. Once this tone is detected by the calling modem the training
sequences begins. Therefore, it usually takes a few seconds before data transfer actually
begins.