23-32-00
 ú ú 06 Page 8 ú Jan 28/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL

 D.  Video Monitors
 (1)  Video monitors are mounted in the passenger cabin ceiling above the main aisle. The forward monitor is retractable and all other monitors are fixed position. Adjustment controls on the monitors are not accessible to flight personnel.
 3.  Operation
_________
 A.  Functional Description (Fig. 2)
 B.  The video system receives ac power from either the right utility bus or the right main bus. Selection of the power source is controlled by the bus switching relay and an air/gnd relay. Circuit breakers for the video system are located on right miscellaneous electrical equipment panel P37. There are two sets of circuit breakers on the P37 panel for the video system. One set of circuit breakers controls the power from the right utility bus. The second set of circuit breakers controls the power from the right main bus.
 C.  Power for the video system from both buses is supplied to the bus switching relay. When the airplane is in the air, the bus switching relay will be deenergized and power from the right utility bus will be supplied to the video system. If the airplane is on the ground, a signal from an air/gnd relay will energize the bus switching relay. The energized relay will supply power from the right main bus to the video system.
 D.  GUN 008-101; Deployment of the passenger oxygen masks will cause a relay within the control distribution unit to energize, removing power from the video system.
 E.  GUN 008-101; The CDU distributes video and audio signals from the VTR. The CDU has the capability to distribute signals from two VTRs and a television tuner (not installed). Distribution of these signals is controlled by the SOURCE SEL switch. As the SEL switch is pressed the VTR light next to the switch comes on and the LED display counts 1, 2, indicating which VTR is supplying the video signals (VTR 2 not installed). Once VTR 2 is reached, pressing the SEL switch again will cause the LIVE light to come on. The LED display will be blank. Pressing the SEL switch again will cause the VTR light to come on and the LED display will show 1. The cycle will continue as the SEL switch is pressed.
 F.  GUN 008-101; The MONITOR SEL switch controls the video source selection for the two inch preview monitor and the audio source selection for the AUDIO MONITOR jack. The switch works similar to the SOURCE SEL switch except that the sequence goes VTR 1 PRI, VTR 1 SEC, VTR 2 PRI, VTR 2 SEC, LIVE PRI and LIVE SEC. Once LIVE SEC is reached, pressing the SEL switch again will cause the VTR and PRI lights to come on and the LED display will show 1. The cycle will be repeated as the SEL switch is pressed.
 G.  GUN 008-101; The master on/off function of the video system is controlled by the SYS POWER switch on the control distribution unit (CDU). The MON PWR switches control the on/off function of all passenger cabin video monitors, provided the monitor is not selected off at the MONITOR CONTROL switches.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH VIDEO ENTERTAINMENT ú

 23-32-00
 ú ú 03 Page 9 ú Jan 28/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

 H.  Video and audio signals are detected by the video tape reproducer (VTR) from the video cassette tape. The video signal is routed to the SCU for distribution to the video monitors.
 I.  GUN 008-101; The video tape reproducer outputs two audio channels to the control distribution unit. The control distribution unit outputs the audio signal to the multiplexer (AMM 23-34-00) which sends the signal to the seat electronics boxes. The seat electronics boxes provide video audio to each passenger seat on passenger control unit channels 1 and 2.
 J.  GUN 008-101; Rotating the control distribution unit PA switch clockwise from OFF provides a PTT-3 signal to the PA amplifier (AMM 23-31-00). This allows video audio to be broadcast over the PA speakers. Audio volume will increase as the PA switch is rotated clockwise. The SEL switch controls whether the primary (PRI) or secondary (SEC) audio channel is provided to the PA amplifier.
　
中國航空網(wǎng) www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：757 AMM 飛機(jī)維護(hù)手冊 COMMUNICATIONS 通訊(58)