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V.25 bis Command Set Operation
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A long space is received and long space disconnect has been enabled by the Yn AT command.
This mode of automatic termination functions only when the modem is operating at 300, 1200,
or 2400 bps.
108.2 Call Establishment Procedure
The general principle for establishing a call between the DTE and DCE complies with the V.25 bis
108.2 mode of operation and is outlined below:
Originating a Call
DTE
Turn On DTR.
Send Command: CRN or CRS.
Wait for the connection (or abort the call by turning Off DTR). Turn Off CTS when answer tone is detected or
Recognize successful connection when DSR comes On.
Recognize connected data rate from the CNX message.
Turn On RTS to send data.
Turn Off DTR to terminate call.
Answering a Call
DTE
Turn On DTR.
Send CIC command to permit answering, or send DIC
command to disregard the incoming ring.
Recognize successful connection when DSR comes On.
Recognize connected data rate from the CNX message.
Turn On RTS to send data.
Turn Off DTR to terminate call.
5-10
ITU-T V.25 bis Command Procedures
DCE
Turn On CTS.
Send VAL response.
Dial phone number.
send CFI response in cases where the call has
failed.
Turn On DSR and DCD when handshake is
successful.
Send connect CNX message.
Enter data transfer mode.
Turn On CTS in response to RTS.
Disconnect from line.
Turn Off CTS, DSR, and DCD.
Send CFI call abort message.
DCE
After detection of an incoming ring, send INC
message.
When Auto Answer is enabled, modem will
answer call after preset number of rings if DTR is
On.
The CIC command is not required.
Disregard incoming ring if DIC is received.
Answer call after the next ring if CIC is received.
At next ring, go off-hook.
Turn Off CTS.
Turn On DSR and DCD when going through
handshake successfully.
Send connect CNX message.
Go into data transfer mode.
Turn On CTS in response to RTS.
Disconnect from line.
Turn Off CTS, DSR, and DCD.
Send CFI call abort message
SpectraComm Dual V.34 Modem
Installation and Operation
060R122-000
Issue 15
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