Service manual

2000 SERIES RECEIVER DECODER MODULE (RDM)
3-8
March 2000
Part No. 001-3139-502
System Key
The system RDMs and all mobiles are pro-
grammed with a unique System Key. The function of
the System Key is to ensure that only authorized users
can access a Multi-Net system. The RDM System Key
is programmed at the factory, and the mobile system
key is programmed into the transceiver by the system
operator. The System Key is a number which is used
by both the RDMs and the mobiles to encode the data
stream. Unless both are programmed with the proper
key, communication is not possible. The System Key
is provided to the system operator by the E.F. Johnson
Company.
Telco Network Type
CIM to RDM voter data signaling.
System Priority Type
Each RDM determines the current system priority
on its channel. The current priority is then transmitted
to its mobiles with other control information. The sys-
tem priority received from the Home repeater and the
access priority programmed into each mobile deter-
mines if a mobile can access the system at that time.
None. No priority is when all mobiles have equal
preference in accessing the system because priority 5
is always transmitted by the repeater.
Reserved Channel. The last available channel is
reserved for exclusive use by Priority 1 mobiles.
Therefore, when only one channel is free, a system
priority number of “1” is transmitted by the repeater.
Next Channel. This priority comes on line only
when all channels in the system are busy. A timed
sequence of access priority is stepped through when a
channel does become available. Priority 1 mobiles are
given immediate access, and then 0.5 second later, pri-
ority 2 mobiles are given access, and so on until 2 sec-
onds later when priority 5 mobiles are given access. A
mobile programmed with a priority number equal to or
greater than the current priority status can always
immediately access the system. If a second channel
becomes available during the countdown sequence, all
mobiles have immediate access.
Both Reserved and Next Channel. This is a com-
bination of the Next Channel and Reserved Channel
priority schemes. When only one repeater is free, it is
reserved for exclusive use by Priority 1 mobiles. When
two channels are free, immediate access is given to both
Priority 1 and 2 mobiles. Then, if two repeaters remain
free for 0.5 second, the stepped access begins. Priority
3 mobiles are given first access, followed by Priority 4
mobiles at the 1-second point, and Priority 5 mobiles at
the 1.5-second point. If during this time, only one re-
peater is again free, stepped access halts and only Pri-
ority 1 mobiles have access. However, if a third
repeater becomes available, all mobiles have immedi-
ate access.
Voter Baud Rate
This is the selectable data rate for voter data,
2400 or 9600 baud.
Test Mode ID
The Group ID that is transmitted when the
Repeater is in the Test Mode. Mobiles with the same
Group ID can communicate with the Repeater in the
Test Mode. The Group IDs are from 1-225, 0 = dis-
abled, the default for Test Mode is 253.
Revert Operation
The revert operation is selected if the RDM local
site has a revert board.
Signal Strength Boundary Indexes
The signal strength boundary indexes define the
boundary points of four contiguous bands in the range
of possible signal strength values. Four indexes are
entered to divide the 5 bands (the outside limits are
fixed). The four values must be in ascending order in
the range from 0-255. Default values are:
Lower Upper
1. Squelched 0 35
2. Weakest 36 41
3. 42 47
4. 48 96
5. Strongest 97 255