CTI Products EXB Network Manager - Manual (Page 9)

Hot-Standby EXB / Network Manager Software Manual Hot Standby
CTI Products, Inc. EXB Operation
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68-11707-100
Central MCN Tie Line This is the MCN network cabling between the Main
EXB and the Standby EXB. Although it is shown as a
single logical jumper in the program and on diagrams,
there may actually be a number of jumpers between the
Main and Standby EXBs, depending upon the exact
equipment mounting.
Remote MCN Tie Line This is the MCN Network Cabling between the two
remote EXB modules in a channel. Although it is
shown as a single logical jumper in the program and on
diagrams, there may actually be a number of jumpers
between the two EXBs, depending upon the exact
equipment mounting.
Control Neuron The processor in the EXB that controls the data flow.
2.2 Operation
The system normally passes data on the Main link. If a failure is detected, the
Standby half of the channel is enabled.
System testing proceeds as follows:
1. The Main EXB module continuously probes its Standby EXB over the WAN
lines.
2. The Standby EXB sends a Probe Acknowledge over the WAN lines.
3. When the Main EXB receives the Poll Acknowledge, it issues a Holdoff
command to the Standby EXB over the Central Tie Line.
4. If the Standby EXB receives the Holdoff command, it will keep its channel
switch turned off. It also sends a Holdoff Acknowledge to the Main EXB.
5. If the Standby EXB does not receive a Holdoff command within a fixed timer
period, it enables its channel switch, passing data to and from the Remote site.
The Hot-Standby EXBs can operate without intervention from the EXB Network
Management Software.
Each EXB in an EXB Channel has custom configured addresses so that the
Control Neuron in the Master and Slave EXBs know the address of each other.
These addresses are entered in the EXB Network Management Software
Configuration Program so that the EXB Network Management Software knows
the addresses of each EXB in a channel.