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This bit is only used when bit 5 is 0 and the modem cannot be switched between calling and
answering mode.
0
The direction is fixed to outgoing and the modem is set in the calling mode (send in the
low band).
1
The direction is fixed to incoming and the modem is set in the answering mode (send in
the high band).
Byte 0 (high convertor speed):
If the modem is used as a convertor in a modem pool, bit 2 of the subsignalling group indicates
if the speed can be switched between the high speed and the low speed by means of CT111
(DSRS). To be able to determine which speed (high or low) is to be used the ISPBX needs a
reference. This reference is byte 0. The Compatibility Value for the data party also holds data
transfer speed. If the CV-speed indicates that the speed of the call is smaller than the speed
indicated by byte 0, the DSRS signal is used to set the modem in the low-speed mode. If the
CV-speed indicates the speed of the call is higher (or the same) than the speed indicated by
byte 0, the modem is set in the high-speed mode.
For each call the calling party-CV is used to determine if the low or the high-speed is to be
used. It the calling party-CV is voice (for instance trunk line) the called party-CV is used
instead.
The relation between the value of this byte and the reference transmission speed is given in
table B.4.
86
only used when modem used as convertor
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