Service manual

6-1
March 2000
Part No. 001-3139-502
CHANNEL RECEIVER VOTER MODULE (cRVM)
SECTION 6 CHANNEL RECEIVER VOTER MODULE (cRVM)
6.1 GENERAL
The Channel Receiver Voter Module (cRVM), at
the Local Site, receives audio directly from the RDMs
at both the Local and the Remote Sites. The cRVM
receives the RSSI level directly from the Local Site
RDMs and through the CDMs for Remote Sites. The
cRVM compares the different Sites and selects the
audio from RDM with the best RSSI value. The
cRVM connects the selected audio to the Repeater
.
Each cRVM can handle the audio from 4-RDMs
and the RSSI level information from 1-Local RDM
and 3-CDMs (or 4-CDMs). There can be 32 possible
Voter Sites, divide this by 4 and 8 is the maximum
number of RVMs required (1-cRVM and 7-slave
RVMs) per channel. For a 30 channel system with 32
Voter Sites, the maximum number of RVMs required
is 240 (30-cRVMs and 210-slave RVMs).
As stated above, a cRVM can have 4 audio/data
inputs (channels). If a fifth Site is added, a slave
RVM is added to each cRVM to accommodate the
fifth Site.
The RVM is powered by +5V DC, -5V DC,
+12V DC and -12V DC. The RVM operates in the
-30°C to + 60°C (-22°F to +140°F) temperature range
with 10% to 90% humidity.
6.2 cRVM TO RVM
The cRVM and RVMs associated with a channel
need to be installed as a group in consecutive slots
within the Voter shelf (see Figure 1-5). This group of
RVMs are independent from the group of RVMs asso-
ciated with another channel. The switches located on
the backplane need to be properly selected to group
cRVMs and RVMs together as required (see Figure
8-3).
The cRVM and RVMs communicate to each
other via the cRVM to RVM bus at 19.2k baud. This
bus needs to be connected between the cards. Connect
the bus by closing section 3 of the switch located on
the backplane between the cards. The proper loading
for this bus is done by closing section 2 of the switch
associated with the cRVM. This loading needs to be
done only to the cRVM or one of the RVMs.
The cRVM or RVMs can connect any one of the
4 possible audio’s it might be receiving to the Receive
Audio path. The cRVM then can connect this Receive
Audio path to the destination card. The Receive
Audio path needs to be connected between the cRVM
and RVMs. This path is connected by closing section
4 of the switch located on the backplane between the
cards.
Refer to Section 8 for the location of the back-
plane switches.
6.3 RECEIVE ORDERS
The RVM receives the initial Receive Call Orders
via a 1200 baud FSK blank and burst signaling on the
main audio line (Refer to Figure 6-1). The RVM
receives the update RSSI information from the
Receiver Decoder Module (RDM) via the RMM and
CDM on the RS-232 input. The RVM handles a maxi-
mum of 4-RDMs and/or 4-CDMs.
The initial Receive Call Orders requires an RSSI
level of "4" to start a call. After the call has been
received, an RSSI level of "3" is required to keep the
call.
The 1200 baud RS-232 input from the CDM con-
tains only the RSSI Level.
Figure 6-1 RVM BLOCK DIAGRAM