BMS Truck-Coder II, Installation And Operation Manual, Page: 10 / 49

2
To simplify installation, only a single coaxial cable is required to interconnect the IDU to the ODU; DC
power, 70MHz IF and telemetry signals are all multiplexed onto this single cable. The system also supports
legacy cable systems that feed DC power on separate conductors.
The indoor unit features a menu driven front panel display (vacuum fluorescent) that is used to configure
the equipment and monitor its performance. The system is also designed to support remote control by 3
rd
party equipment using either web based or simple RS232 protocol.
The outdoor RF unit (ODU) is designed to be mounted outdoors adjacent to the antenna. The ODU
translates the 70MHz IF signal from the IDU (exciter) to the desired operating frequency and amplifies the
signal to the desired level. The RF unit employs automatic level control circuits that keep the system
operating optimally and eliminate the need for any user adjustments.
The ODU uses a common signal path for both Analog (FM) and digital (COFDM) operation. Performance
is automatically optimized for both methods. BMS transmitters feature superior COFDM performance that
is adequate to support split channel operation in a 12MHz channel (
see BMS white paper ).
The ODU provides signals to control an antenna relay and feed polarity. Additional contact closures are
also provided for user specific applications.
A more detailed description follows:
Indoor Unit
A simplified block diagram of the IDU is shown below:
Figure 2 TCII IDU (Indoor Unit) Block Diagram