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The Option Switches
The Option switches allow you to control the operation of your modem in Dumb mode, as well
as providing additional features in Smart mode.
For users of modems with front panel Option switches only
• Front panel Option switches 1 and 2 always take precedence over software setting of
behaviour of DTR and DSR. When AT%F is set to 1 (when AT%F is set to 0, behaviour of
DTR and DSR is controlled by AT commands if applicable).
Switches 1 and 2 are used to select AT command mode or V.25bis command mode, or control the
state of the DTR and DSR signals.
Description AT%F Switch 1 Switch 2
AT command mode %F0 Up Up
V.25bis asynchronous %F0 Up Down
V.25bis synchronous (HDLC framing) %F0 Down Up
V.25bis sync (BSC character framing) %F0 Down Down
DTR controlled by computer %F1 Up n/a
DTR assumed to be asserted (raised) %F1 Down n/a
DSR acts normally %F1 n/a Up
DSR mimics DTR %F1 n/a Down
☞ n/a = not applicable
Switches 3 - 6 allow you to set up Dumb mode operation, as well as manually selecting
loopback tests in Smart mode.
Description AT#F Switch Switch
Smart mode n/a 4 - Up n/a
Dumb mode n/a 4 - Down n/a
Loopback Test Pattern Off #F 1 3 - Up 4 - Up
Loopback Test Pattern On #F1 3 - Down 4 - Up
Analog Loopback Off #F1 5 - Up 4 - Up
Analog Loopback On #F1 5 - Down 4 - Up
Remote Digital Loopback Off #F1 6 - Up 4 - Up
Remote Digital Loopback On #F1 6 - Down 4 - Up
Auto-answer enabled n/a 3 - Up 4 - Down
Auto-answer disabled n/a 3 - Down 4 - Down
Asynchronous operation n/a 5 - Up 4 - Down
Synchronous operation n/a 5 - Down 4 - Down
Answer mode n/a 6 - Up 4 - Down
Originate mode n/a 6 - Down 4 - Down
+ n/a = not applicable