Broadcast Electronics Marti GRX, User And Maintenance Manual, Page: 21 / 45

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INSTALLATION
Rack Mounting and Cooling
It is very important to install the apparatus on a stable stand/rack, in such a way to permit good
ventilation to the rear heatsink
Since the STL equipment is cooled by convection in air, allow a 1RU clearance above and below the
equipment. This especially important for heat sink in the rear of the transmitter
Control Functions
Both the STL Transmitter and Receiver are set and controlled by the front panel keyboard and
display. The same functions can be remoted via the parallel control port and a future serial RS232
port. Both of these 2 ports are located in the right rear of the Transmitter and Receiver.
Remote Control Parallel Port
This is the primary port to accommodate control and monitoring functions on this DB9 male
connector. Many of the I/O lines may be assigned to different functions and logic polarity may be
changed as needed for the sites remote control equipment. Default pin assignment is listed in Section
3.2 for the Transmitter and Section 3.3 for the Receiver.
RS232 Port (Factory)
The RS232 port is a factory connection location for installing software control options. Other than
this use, no connection is required to this port for installation.
Figure 4 - GTX & GRX Remote Connectors
GTX Parallel Remote
Pins 1, 5, 8 Ground.
Pin 2, “On Air” output. Open collector transistor circuit with a resistive pull-up: at +12V
10kOhm signals that the transmitter delivers substantial RF power. It is not granted that the output
power is exactly as preset.
Pin 3,
Forward power output. A signal proportional to forward power, aka direct power,
with a pseudo square law. Range is 0-5Vdc / 1k  impedance. Full power voltage ranges 3,5 to 4 V.