DSP9612RM USER’S GUIDE
0049-0519-000
Page 12
REV.D
SW2-1
⎯
FSK Mode
SW2-1
ON = ITU-T V.23 mode
OFF = Bell 202 mode
The modem has two FSK modes:
Bell 202, which supports data rates from 0 to 1800 bps
ITU-T V.23, which supports data rates from 0 to 1200 bps
SW2-1 configures the modem for either of these FSK modes. Setting SW2-1 to
ON selects ITU-T V.23 mode. In this mode, the modem complies with ITU-T
(CCITT) recommendation V.23 with the following parameters:
Mode 2 modulation only
No backward channel
No provisions for disablement of echo suppressors
DTR (circuit 108) is ignored
Setting SW2-1 OFF selects Bell 202 mode.
SW2-2
⎯
Receiver Squelch (FSK Mode 2-Wire Half-Duplex Only)
SW2-2
ON = 8ms for Bell 202, 150ms for ITU-T V.23
OFF = 0ms
SW2-2 configures the turnaround squelch delay and is valid when the following
are active:
FSK mode (SW3-1 ON)
2-wire half-duplex operation (SW3-7 ON)
Setting this switch to OFF configures the modem to enable its receiver
immediately after the Request To Send (RTS) signal is turned off. When this
switch is set to OFF and the modem is configured for 2-wire, half-duplex mode
(SW3-7 ON), the modem squelches the receiver after RTS is turned off to prevent
far-end echoes from causing data errors. The duration that the modem squelches
the receiver is either:
8 milliseconds if the modem is configured for Bell 202 mode (SW2-1
OFF)
150 milliseconds if the modem is configured for ITU-T V.23 mode (SW2-
1 ON)
