777 AIRCRAFT MAINTENANCE MANUAL
VHF SYSTEM -RADIO TUNING PANEL
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VHF SYSTEM -AUDIO CONTROL PANEL
General Description
The audio control panel (ACP) supplies transmitter selection, receiver selection and volume control for the left, center, or right VHF communication transceiver. The VHF controls are on the upper half of the ACP.
Control and Indications
Push a VHF receiver volume control to listen to a VHF receiver. Rotate the receiver volume control for volume control. The receiver light above the control shows green with the receiver control on.
Push a transmitter select switch to select a transceiver for transmission. The mic light shows green for the selected system. Push the mic/interphone switch to connect the microphone to the transceiver and key the transceiver.
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777 AIRCRAFT MAINTENANCE MANUAL
VHF SYSTEM -AUDIO CONTROL PANEL
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777 AIRCRAFT MAINTENANCE MANUAL
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VHF SYSTEM -TUNING FUNCTIONAL DESCRIPTION
General Description
During tuning, the radio tuning panel (RTP) sends signals to a selected transceiver, to the other two RTPs, and to the airplane information management system (AIMS). Each radio tuning panel (RTP) operates in the same way. This example shows the right RTP and the on-side transceiver.
Input Data Buses
The other two RTPs send tuning data on the crosstalk buses to RCVR 1 and RCVR 2 in the right RTP. The transceiver uses this data to tune the transceiver from an off-side RTP.
The AIMS cabinets send auto-tuning data on an auto-tune bus to RCVR 3 and RCVR 4. The RTP uses the auto-tune data to update the RTP standby frequency.
The ARINC 429 port relay in the right RTP selects either the right RTP or the center RTP as the source of tuning data. This goes to the port A input of the right VHF communication transceiver and the port B input of the left and center VHF communication transceivers. If the right RTP fails or is off, the center RTP tuning data goes to the tuning bus. The port select switch in the right communication transceiver then selects the port B input. The port B input is from the left RTP. This tuning bus input is from the left or center RTP. The ARINC 429 port relay in the left RTP determines this.
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Discrete Inputs
The discrete input processor changes discrete inputs to digital data and sends it to the microprocessor. Discretes the RTP uses are:
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Program pins -gives position information of each RTP. This information tells the right RTP how to operate with respect to the other RTPs.
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Test (MD&T) -master dim and test input turns on all RTP front panel lights and annunciators
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Front panel switches-control switches on the RTP front panel.
Output Data Buses
The right RTP microprocessor sends tuning data to XMTR 1. It sends the data through the ARINC 429 port relay and, on the tuning bus, to port A of the right transceiver. The data goes through the port A ARINC 429 RCVR and through the closed port select switch to the microprocessor. It sends this tuning data to the frequency synthesizer to tune the transceiver.
Manual Tuning
The frequency selectors send frequency values to an encoder processor. The processor changes the values to digital data and sends it to the microprocessor. The microprocessor sends frequency window data to the LCD drivers and LCD displays. It also sends the frequency data through XMTR 1 to the right transceiver on the tuning bus.
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VHF SYSTEM -TUNING FUNCTIONAL DESCRIPTION
The tuning data from the right RTP also goes to the left and center RTPs on the crosstalk bus.
The nonvolatile memory (NVM) keeps the tuning data when the RTP is off.
Auto Tuning
Auto-tune buses from AIMS carry tuning data to RCVR 3 and RCVR 4 in the right RTP. The RTP microprocessor uses the autotune data to update the RTP standby frequency. The microprocessor also energizes or de-energizes the ARINC 429 port relay. The port select relay sends an open or a ground to the right transceiver to select port A or port B for tuning data.
Default Tuning
When the right RTP is off, the ARINC 429 port relay de-energizes. The center RTP sends tuning data directly through the right RTP to the radios and to AIMS. The right VHF transceiver gets tuning data in port B from the left RTP.
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