Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
RFL 9785 RFL Electronics Inc.
June 18, 2009
2-11 (973) 334-3100
either the input or output of the filter, several filters are available, several with jumper-selectable sub-
bands. This provides an easy and accurate method of setup. See Section 9 for more information about
the Output Filter Module.
The output of the transmitter circuits must be fed out to the field wiring. This is accomplished using a
Line I/O Module. The module provides a UHF connector for Tx and another for Rx. It also contains
protection circuitry. See Section 18 for more information about the Line I/O Modules.
One significant alteration to the transmit description above is when an external power amplifier is
used. This may be required if more than 10 watts of output power is needed. In this case, the Power
Amplifier Module is omitted from the chassis. Additionally, there would be no need for the 9785
Output Filter or Hybrid, as these would be required after the external power amplifier.
2.8.2 RECEIVER SECTION
The function of the receiver section is to detect a carrier signal sent by the remote transmitter. The
receiver consists of a Line I/O Module, a Downshifter Module, a Receiver Detector Module, and an
AM Logic Module.
The received signal enters the 9785 chassis through a Line I/O Module. The Line I/O module has two
UHF connectors, screw-type terminal connections, impedance matching circuits, and ANSI C.37.90
compliant protection circuits. See Section 18 for additional information regarding the Line I/O module.
The signal is then fed to the Downshifter Module. This module normalizes the received level and shifts
the received carrier from the customer specified center frequency down to the 9785’s baseband
frequency of 24KHz. Its channel filter has a 3700 Hz bandwidth to pass voice sidebands if the voice
option is installed.
The Receiver Detector Module accepts the signal produced by the Downshifter Module, and passes it
through a narrow-band filter. A decision whether or not to block is based upon this signal strength. The
Receiver Detector Module is equipped with a voice bandpass filter and voice muting circuitry if the
voice module is installed. The signal is also sent to a log amplifier circuit to convert the level to a dB
measurement.
The block signal is sent to the AM Logic Module. The received block signal drives open-collector
transistors, energizing associated solid-state and electro-mechanical relays. Since the received block
signal may be a voice transmission from the remote carrier, the local carrier voice is muted until the
received block ceases. This is known as simplex communication. A locally keyed block also mutes
voice received from the remote carrier. The block signal may also be communication between master
and slave Checkback modules. The block ON/OFF pulses are interpreted as messages.
To Next Page
Loading...
