Glenayre Document Number: 9110.00148
RL-903 Receiver
Issue
1, Rev. C:
12/10/96
THEORY OF OPERATION
Green front-panel SQUELCH LED D14 lights whenever the receiver is unsquelched.
Front-panel NORMAL SQUELCH control R80 adjusts the sensitivity of noise squelch.
Front-panel
TIGHT SQUELCH control R81 adjusts the sensitivity of carrier squelch.
Refer to Paragraph 7.7 for adjustment.
The RSSI signal from U2 goes to dc amplifier U6-1 and comparator U7-7. The RSSI
voltage is available at rear-panel J1-12 (TB3-5) for external equipment.
6.4.4
Fault Reporting
A condition which causes the receiver's PLL circuitry to go out of lock, causes the lock-
detect signal at P3-8 to go LO. The fault causes a HI at Q2-drain and rear-panel J1-14
(TB3-4) for reporting to external equipment. During a fault, D5 causes the receiver to be
squelched.
6.4.5
Keying
The receiver must use the optional tone board for keying. Green front-panel KEY LINE
LED D11 lights whenever the keyline is active. The front-panel key switch works as
follows:
• S 1 set to REMOTE. A keytone* LO from the tone board at P6-3 is passed, via front-panel
KEY switch S1, to U7 and Q4. A LO to the paging or link transmitter is passed to rear-
panel txkey* J1-3 (TB3-1). The receiver must be unsquelched in order for the keyline to
become active.
• S1 set to DIS. Keying is disabled.
• S1 set to KEY. The txkey* output is active (LO).
6.5
Line Driver Circuit (optional) (IF board)
Refer to Figure 3-4, Receiver Functional Diagram. The line out audio input at front-panel
LINE OUT control R57 is amplified by op-amp U8-1 and drives transformer T1, whose
balanced output exits the chassis at rear-panel J1-10 and -15 (TB2-7, -8). Comparators
U8-7 and U8-8 control front-panel HIGH and OK D15. Refer to Paragraph 7.7 to adjust
level.
Print Date: 12/05/96
Copyright © 1996 Glenayre
Page: 6-5