Chapter 7: Service and troubleshooting
128 P/N 3101890-EN • REV 006 • ISS 21JUN18
Figure 41: Network wiring alternating between channel A and B
(1) Cl
ass B network wiring one-line diagram
(2) Class A or Class X network wiring one-line diagram
When multiple VM-CPU modules are networked together using Class B wiring, the network data LEDs should
flash on all panels except the first and last panels. This indicates normal two-way network communication activity
on both data channels.
When multiple VM-CPU modules are networked together using Class A or Class X wiring, the network data LEDs
should flash continuously. This indicates normal two way network communication activity on data channels A
and B.
The data network and digital audio risers are isolated at each VM-CPU. This prevents a shorted data circuit from
interrupting communication on the entire circuit.
When trying to isolate trouble on a data network or digital audio riser, remember that both shorted and open
circuit segments will interrupt communication between two VM-CPU modules. In this case, the VM-1 life safety
network will reconfigure and operate as two independent sub-networks
Due to the isolation between cabinets, during a ground fault condition the number of potential circuits to be
investigated is limited to those originating from a single cabinet.
Table 45: VM-CPU Main Board troubleshooting
Possible cause
DS9 (RX) and DS10 (TX) or
11 (RX) and DS12 (TX) off, or
• The TB5 network wiring + and − is reversed
• A circuit was not properly terminated
• The network A and B circuits are crossed
• An improper wire was used
• A ground fault has been detected
• The VM-NOC card is not seated properly
-232 device wired to
5 inoperative
• The TX and RX wires are reversed
•
The VM-CPU and peripheral device baud rate are mismatched
•
The peripheral device is off-line or improperly configured
A B
CPU
(1)
(2)
A B
CPU
A B
CPU
A B
CPU
A B
CPU
A B
CPU
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