L36588K75879
ATC System Component Location 5C8
34-53-0 Figure 1 (Sheet 1) Jun 20/85
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5C8 ATC System Component Location
Jun 20/88 Figure 1 (Sheet 2) 34-53-0
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
E. On GJ B-2509 and B-2510, the position of the function switch determines the operational status of the transponder. The switch has four positions; OFF, STBY, ON and LO SENS. The switch can be turned directly to ON and after approximately 80 seconds warm up delay, power will be applied to the transponder circuits. The LO SENS position provides operation at reduced gain. The mode switch, with positions A, B, C, and D selects the interrogation signal from the ground to which the transponder will reply. In mode A, the transponders will respond to an interrogation signal with a pair of pulses spaced at an 8 microsecond interval. The modes B, C, and D are not used but can be activated for different spacing intervals at a later date. The position of the transponder selector switch, selects the corresponding transponder while the other transponder is in standby.
F. The control module receives a 0-5-volt ac signal from the lights dimmer control through the 5V AC SEC circuit breaker on the P8 panel (Ref Chapter 33, Pilots' Panel Lights).
3. ATC Transponder
A. All electrical connections to the transponder are made through a connector located on the lower portion of the rear panel. The connector located on the upper portion of the rear panel is used to connect automatic test equipment to the system.
B. Controls and indicators mounted on the front panel of the transponder are a SELF-TEST button and reply light (combined), R/T and ANT fault indicators, and RESET button. The SELF-TEST button and reply light are functionally paralleled to the TEST button and REPLY light on the ATC control panel. The R/T and ANT fault indicators are ball type indicators which rotate to display the yellow side to indicate a malfunction. The black display indicates a no-fault condition. The RESET button is used to reset the ANT fault indicator to a no-fault condition.
4. Antenna
A. The two ATC antennas are conventional blade-type units connected to the transponder (s) by coaxial cable. Each antenna performs the transmitting and receiving functions for its respective transponder (if installed).
5. Operation (Fig. 3)
A. Basic ATC Transponder Principles
(1)
The transponder is an integral part of the Air Traffic Control Radar Beacon System (ATCRBS). In the airplane, its function is to transmit a coded response to a coded interrogation transmitted by the air traffic control ground station.
(2)
There are two types of radar at each of these ATC ground stations. The first, called the Primary Surveillance Radar (PSR), operates on the normal radar principles of receiving energy reflected from the airplane under surveillance. The second, called the Secondary Surveillance Radar (SSR), operates on the coded reply from the airborne transponder. Both radars are used in conjunction to develop the total air traffic situation and to display it on a single radar scope.
(3)
The SSR interrogates the transponder in one of two modes. These are referred to as mode A, or mode C interrogations. The type of interrogation is determined by the spacing between two pulses (P1 and P3) transmitted by the SSR on a carrier of 1030 士2 MHz. Each interrogation contains a third pulse at the same frequency which is not transmitted by the SSR but by an omnidirectional antenna which is located at the ground radar station. This pulse is transmitted 2 usec after the P1 pulse and is referred to as P2. Mode A and mode C interrogation characteristics are shown in Fig. 2.
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