13.3.1.1 SINGLE-CHANNEL MODEM OPERATION
If the RFL 9300 contains an RFL 93B MO Modem Module in the first module slot, the RFL 93B CC module will
initialize and reset the modem over a dedicated sixteen-bit bus. Control bits in the RFL 93B MO module are set
or cleared to configure the modem for CCITT V.29 operation at 7.2 Kbps.
Modems occasionally require training from the remote RFL 9300; when necessary, training request messages
are generated in the RFL 93B CC module. The words passed between the RFL 93B MO and RFL 93B CC mod-
ules at both units are synchronous and serial. The squelch rules that define word validity depend on the com-
munication system; the modem rules are tested with each received word. These rules also determine if an alarm
should be sent to the RFL 93B SV module, or if the serial communications coming in from the modem needs to
be framed.
13.3.1.2 HOT STANDBY TWO-CHANNEL MODEM OPERATION
If the RFL 9300 contains a second RFL 93B MO modem module in the second module slot and the system is
not configured for three-terminal operation, it is configured for hot standby operation. The RFL 93B CC module
in the third module slot learns the system during turn-on and controls both modems. It sends and receives ini-
tialization and training commands to maintain communications over both modems. The RFL 93B CC module
controls the channels and automatically switches if the active channel fails. After switching over, the RFL 93B
CC sends a message to the remote RFL 9300; when the remote RFL 9300 receives this message, it will switch
its modems. In every other way, the RFL 93B CC module acts the same as single-channel modem operation.
13.3.1.3 SINGLE-CHANNEL 56-Kbps OR 64-Kbps DIGITAL OR FIBER OPTIC
OPERATION
If the RFL 9300 contains an RFL 93 DD Direct Digital I/O Module or an RFL 93 FT/FR module, the RFL 93B CC
module learns the communication configuration based on the clock rate received and the strap settings passed
over from the RFL 93B SV. The RFL 93B SV uses modified high bit-rate squelch rules and alarm conditions.
Each word is repeated three times during transmission, and a voting scheme determines validity. The remote
RFL 93B CC module super-frames on the blocks of three, and uses two-out-of-three voting logic. Direct digital
operation is synchronous, with the transmit and receive clocks supplied by the data communication equipment
(DCE). A port for TX DATA and RX DATA is also provided.
13.3.1.4 HOT STANDBY TWO-CHANNEL 56-Kbps OR 64-Kbps DIRECT DIGITAL
OPERATION
If the RFL 9300 contains two RFL 93 DD Direct Digital I/O Modules, the RFL 93B CC module learns the com-
munication configuration based on the clock rate and the strap settings passed over from the RFL 93A SV mod-
ule. The RFL 93B CC modules in both RFL 9300's use high bit-rate squelch rules and commands to control
switchover if a channel should fail several frame attempts.
NOTE
Refer to Table 2-1 for valid Hot-Standby configurations
RFL 9300 RFL Electronics Inc.
February 7, 2000 13 - 5 (973) 334-3100
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