RFL 9780 RFL Electronics Inc.
April 8, 2003 4-9 (973) 334-3100
4.7.1 LINE TERMINATION
The 9780 receiver section can be configured to terminate the incoming line or not. Note that the input
of the RF Interface Module is a high impedance input. The termination and protection circuits are
located in the Line I/O assembly in the rear of the unit. To change the termination setting, the Line I/O
Module must be removed from the chassis and the jumper selected for “50Ω” “75Ω” or “OUT”. If the
receive sections of several chassis are interconnected; only one of them should be terminated. Note that
the termination impedance is only specified up to one watt maximum. See Section 17 for more
information.
Also note that if a hybrid is installed inside the unit, the hybrid can provide the required impedance
matching and circuit protection.
4.7.2 RECEIVE FREQUENCIES
The user must know the carrier center frequency, the frequency shifts, and whether a shift-up indicates
a guard or a trip. Once the center frequency is known, the RF Interface Module must be properly
configured. This module is a 10 KHz bandpass filter that helps remove unwanted energy from the
incoming signal. The receive center frequency is configured using switches SW1 through SW4; see
Paragraph 11.4.3 for more information.
The receive center frequency must also be programmed into the IF/BF module which is used to
translate the received signal down to the desired 4 KHz baseband frequency. This is accomplished
using switches SW1 and SW2, see paragraph 12.4.1 for more information.
The bandwidth of the received signal (twice the frequency shift) determines which CLI and LM/SL
Modules are required in the system:
A 200 Hz bandwidth system (±100 Hz shift) requires:
one 106430-1 200 Hz BW CLI Module and
one 106430-1 200 Hz BW LM/SL Module for 60 Hz grids,
OR one 106430-11 200 Hz BW LM/SL Module for 50 Hz grids.
A 500 Hz bandwidth system (±250 Hz shift) requires:
one 106430-2 500 Hz BW CLI Module and
one 106430-2 500 Hz BW LM/SL Module for 60 Hz grids,
OR one 106430-12 500 Hz BW LM/SL Module for 50 Hz grids.
A 1000 Hz bandwidth system (±500 Hz shift) requires:
one 106430-3 1000 Hz BW CLI Module and
one 106430-3 1000 Hz BW LM/SL Module for 60 Hz grids,
OR one 106430-13 1000 Hz BW LM/SL Module for 50 Hz grids.
Additionally, the system must be configured to properly interpret the frequency shifts. Switch SW2-8
is used to select shift-up or shift-down for trip. See paragraph 6.4.17 for more information.
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