RFL 9300 RFL Electronics Inc.
October 29, 2001 2 - 5 (973) 334-3100
2.3.2 HOT STANDBY TWO-CHANNEL MODEM OPERATION
If the second module slot in the RFL 9300 chassis contains another RFL 93B MO Modem Module and the sys-
tem is not configured for three-terminal operation, the Communications Controller will control both modems. The
RFL 93B CC "learns" the configuration while initializing. During normal operation, communications with the re-
mote RFL 9300 are maintained over both channels. The RFL 93B CC monitors the channels and switches to
the other channel if the active channel fails. After the switchover, the RFL 9300 sends a message to the remote
RFL 9300 , asking that it also switch to the other channel. In all other respects, hot standby operation is identical
to single-channel modem operation. Hot standby mode is not available if the relay is configured for 3-terminal
operation.
2.3.3 SINGLE-CHANNEL 56/64-Kbps DIGITAL OR FIBER OPTIC OPERATION
The RFL 9300 is equipped with an RFL 93 DD Direct Digital I/O Module, a Fiber Optic transceiver module or a
G.703 module when high-speed digital communications are required. The RFL 93B CC will "learn" the system
configuration from the received clock rate and strap setting information received from the RFL 93B SV module.
The alarm conditions and squelch rules used during high-speed operation are different from those used during
modem operation. Each word is transmitted three times, and the receiver uses a two-out-of-three voting scheme
to determine if a received message is valid. Direct digital operation requires a synchronous clock to be supplied
by external data communications equipment (DCE), and ports for TX and RX data.
2.3.4 HOT STANDBY TWO-CHANNEL 56/64-Kbps DIRECT DIGITAL OR FIBER OPTIC
OPERATION
For two-channel, high-speed, hot standby applications, a pair of RFL 93 DD Direct Digital I/O Modules, a pair of
Fiber Optic transceiver modules, or a pair of G.703 modules are plugged into both rear chassis communications
slots. The local and remote RFL 93B CC modules "learn" the configuration during initialization, and employ
high-bit rate squelch rules to command channel switchover if a channel should fail several frame attempts. Hot
standby mode is not available if the relay is configured for 3-terminal operation.
2.3.5 HOT STANDBY CONFIGURATIONS
In 9300 applications that use the hot standby feature, some limitations must be kept in mind if the communica-
tion medium at Channel 1 and Channel 2 are different types. The limitations are due to differences in the clock
sources used by the communication medium. Refer to Table 2-1 for valid hot standby configurations.
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