3810-rwt.ib.rev1.doc
Page 4 of 11
17/10/2007
RWR-3810 Photo-diode Receiver.
The RWR-3810 photo-diode receiver module consists of an optical detector diode circuit with integral pre-
amplifier. Integrated attenuator and discrete amplifier circuits follows to set the output RF level of the system.
A RF gain control and RF monitor connector are provided on the front panel. The gain of the RF amplifier is
adjusted by the front panel control (RV3), which varies the bias on the attenuator circuit in the RF gain stage. The
RF level can be varied from –45dBm to –20dBm at the output RF connector for a correctly modulated RWR-3810
transmitter. The RF level at the front panel monitor connector is set at the same level as the rear panel RF output,
this allows the RF level to be checked as the RF gain is adjusted. This output should be terminated with the 75 ohms
termination provided when not in use.
The bias current of the optical detector diode is connected to a comparator circuit, which is used to provide received
optical signal indication. The circuit will light indicator lamp LD3 on the front panel for OPTICAL SIGNAL
indication (green for normal and red for failure), and with LK1 closed will operate a relay circuit, an ALARM
contact set is available as an external connection. The adjustment and connection data for this circuit is given in the
installation section of the manual.
A 10.7 MHz pilot tone detector circuit is provided which with the pilot generator circuit in the RWT-3810
transmitter will verify the RF signal path of the system. The pilot tone level is monitored by a detector circuit whose
output will be indicated by LD2 (green for normal and red for failure), and can, by closing LK2, operate the alarm
relay circuit if a failure occurs.
The power supply comprises two bridge rectifiers whose rectified outputs are paralleled (positive and negative
respectively) to provide redundancy. The inputs to these rectifiers are two independent feeds of 28 Vac (centre tap
grounded). The rectified DC are regulated by three-terminal regulators. The LED on the front panel is wired in
series with a zener diode b12 and -5.2 Volts. The zener is to ensure that the LED extinguishes if any one of
the regulators fails.
NOTE:
Direct connections are made to the rear of the RWT-3810 and RWR-3810 modules for the
OPTICAL and RF cabling, these must be disconnected when a module is to be mounted or removed from the
IRT Eurocard mounting frame.
IRT
Communications
www.irtcommunications.com
