G.  The chassis contains ac and dc power supplies, rear connectors, front panel controls and indicators and interconnect board. The front panel components include phone and microphone jacks, a SQL/LAMP TEST PUSHBUTTON, AND R/T FAULT and KEY INTERLOCK lamps. The ac power supply, mounted in the lower tray, converts 3-phase, 115-volt, 400-Hz input power into 46- and 28-volt dc power. The dc power supply, mounted in the upper tray, contains regulators that produce +5-, +10-, +11-, and +20-volt dc power. The interconnect board contains input audio amplifier, fault monitoring, and key interlock circuits.
H.  Front Panel Controls and Indicators
(1)  
The front panel of the transceiver has two lamps and a pushbutton switch. The front panel of the adapter has a 2-position switch that is operated using a screwdriver.

(2)  
The two lamps on the transceiver are the KEY INTERLOCK and R/T FAULT lamps. The KEY INTERLOCK lamp will light when keying transmitter if the external antenna coupler has failed to tune properly. When this lamp is on, transmission is inhibited. The R/T FAULT lamp will light when the internal monitoring circuit detects a transceiver fault. The faults that will light this lamp are: the frequency synthesizer is out of lock; lock transmitter power output (60 watts pep nominal threshold) in AME transmit mode; and low voltage from the +5-, +10- or +20-volt dc power supplies.

(3)  
The pushbutton switch on the transceiver is the SQL/LAMP TEST switch. When pressed, the KEY INTERLOCK and R/T FAULT lamps should light and the squelch circuit is disabled.

(4)  
The switch on the adapter is the SQUELCH/RF SENS switch. This switch must be positioned so that the transceiver will interface properly with the particular type of remote radio set control that is being used.

4.  Transceiver Adapter
A.  The adapter is used to adapt the transceiver, to the mounting and wiring provisions existing in present airplane configurations.
5.  Coupler Status Annunciator Panel
A.  The coupler status annunciator panel located in the electronic equipment area, contains 10 indicator lights. The panel provides remote visual indications of faulty HF system operation. Five indicator lights are for HF system No. 1, and five identical indicators are for HF system No. 2. A decal adjacent to the indicator designates the system and circuit function for each set of the following five indicators:
(1)  
COUPLER FAULT - A failure of the coupler to home or tune the circuits within 15 seconds causes the indicator light to come on.

(2)  
RF FAULT - The following cause the indicator light to come on: transceiver malfunction, an open coaxial cable, or insufficient power. These faults all indicate a lack of RF power.

(3)  
PRESSURE FAULT - Low pressure in the coupler causes the indicator light to come on.

(4)  
TUNE IN PROCESS - Using the coupler in a tune mode causes the indicator light to come on.

(5)  
OPERATE - Placing the coupler in an operate condition causes the indicator light to come on.

5C8
Jun 20/85 23-11-01 Page 5
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

B.  Each indicator has a self-test feature which operates to check the lamp when the indicator shroud is pushed in. Both sets of indicators receive 28V dc from the respective antenna coupler when power is applied to the system. When the coupler senses a fault, the sequence counter freezes and operates the fault circuit to provide a ground return that causes one of the three fault indicator lights to come on. The TUNE IN PROCESS indicator receives a ground return from the coupler to cause the indicator light to come on whenever a tuning sequence takes place. The OPERATE indicator receives a ground return after the coupler has completed a sequence of home, standby, and tune, and is in the operate condition.
6.  Antenna Couplers
A.  Two identical antenna couplers are located at approximately station 1016 just below the HF antenna vertical fin leading edge. The coupler has miniaturized transistor circuits contained in a rack-mounted pressurized case. Electrical connection is provided through two multipin connectors located on the front of the unit. The RF connection is through a coaxial plug designated RF INPUT located on the front panel. The antenna connection is at the rear of the unit.
B.  The pressurized case has two sections divided by an RF shield which provides thermal protection as well as RF isolation. The forward compartment contains tuning control modules, a dual servo-amplifier, and the power supplies. Integrated circuit construction is used in the servo-amplifier and tuning control modules. The rear section of the coupler (the RF compartment) contains the tuning element, a discriminator module, and an isolation amplifier. The tuning elements consist of two variable vacuum capacitors and a variable inductor, associated motors, gear trains, switches, and RF relays.
　
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