Control Unit IV Reference Manual Troubleshooting
529-0004 Ver.3 6-9
COM 2
In a redundancy system, both Control Units are connected together on COM 2 in order to
synchronize the content of their internal subscriber status database. Only the backup unit
receives data on this COM port. It stores the same information as the master unit so that if an
error occurs and the two units switch roles, then the backup unit will be up to date.
Normally, the
RX
/
TX
2
LED should light up on the backup unit when it is checking the
presence of the master unit. The
RX
/
TX
2
LED on the master unit should remain off.
If the
RX
/
TX
2
LED on both units flash at startup, then each unit has not detected the presence
of the other unit. They will both send a handshaking message, which will cause an error on
each unit. The
RX
/
TX
2
LEDs will light up briefly at each error. To troubleshoot the problem,
make sure that the redundancy cable is properly plugged in on both units. If the problem
persists, reset the redundancy circuitry (see section 6.4.3).
COM 3
Whether a Control Unit is used alone or in conjunction with another unit to ensure
redundancy, COM 3 is used for setting up the Control Unit. This port can also be used for
manual subscriber control, using the Control Unit’s internal program through a terminal. For
diagnostic purposes, you may want to keep a terminal connected at all times.
Note for redundancy system:
If you manually make changes to a subscriber’s status through this port, you must make
the same change on the backup unit in order to ensure that both units are identical.
If the
RX
/
TX
3
LED does not flash when you enter a command through a terminal connected
to COM 3, check the terminal’s settings (see Chapter 3). The communication parameters on
COM 3 cannot be changed.
6.4.2 RF ports in a redundancy system
In a redundancy system, only the master unit transmits the data carrier signal on its
RF OUT
port. If the RF watchdog detects an error with the master unit, a toggle occurs and the backup
unit will then transmit the carrier on its
RF OUT
port.
A short coaxial jumper cable must be connected to the
TEST IN
and
TEST OUT
ports on each
unit. This ensures that the RF watchdog can monitor the modulator. If the RF signal fails on
the master unit, the backup unit can take over. You should set the RF watchdog to 254 in
order to ensure that the toggle takes place (see Chapter 3).
If the Control Unit is set up to toggle the redundancy circuitry on error and the coaxial
jumper is not connected on the
TEST IN
and
TEST OUT
inputs of a Control Unit, the unit will
continue to reset until the cabling problem is corrected.
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