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Chapter 5: Configuration
56 ISU 512 User Manual 61202.086L1-1
CONFIGURING THE ISU 512 FOR V.25 BIS IN-BAND DIALING
V.25 bis dialing is used primarily by data terminal equipment with synchro-
nous interfaces (HDLC/SDLC or BSC/BISYNC) not supporting the AT com-
mand set, which is commonly used by asynchronous devices. The ISU 512
supports V.25 bis in-band dialing in accordance with Fascicle VIII.I - V.25 bis
(Malaga-Torremolinos 1984, Melbourne 1988).
Recommendation V.25 uses the following DCE/DTE control signals:
Transmitted data Circuit 103
Received data Circuit 104
Ready for sending Circuit 106
Data set ready Circuit 107
Data terminal ready Circuit 108/2
Calling indicator Circuit 125
The ISU 512 supports the following V.25 bis commands to control automatic
calling and answering:
CRN Call request (number in command)
CRS Call request (using stored number)
PRN Program stored number
RLN List stored number
CIC Connect incoming call
DIC Disconnect incoming call
When using stored numbers, V.25 bis accesses stored numbers 1 through 9 used by
front panel dialing. See Dialing Options (in this chapter).
Auto answer should be disabled if V.25 bis is in control of answering incoming calls
with the CIC/DIC commands, since the other settings for Auto answer will override
V.25 control of the answer function.