User's Manual Part 2

T
2
CAS / Part No. 9000000
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
34-43-20
15 Feb 2003
Use or disclosure of information on this page is subject to the restrictions in the proprietary notice of this document.
4--3
Table 4--1. TT--950/951/952 T
2
CAS Computer Unit Interface Description (cont)
Connector Pin
Designation
Functional Description
RMP--2E Spare Pin
RMP--2F, 2G 8 Ohm Audio Output: (RMP--2F [HI], RMP--2G [LO])
This is a synthesized voice output supplied by the T
2
CAS computer unit. Its level is
programmable up to 8 Watts into an 8 Ohm speaker. All aural traffic and resolution
advisories are announced over this output. See RBP--7A for audio level programming.
RMP--2H, 2J Radio Altimeter No. 1 ARINC 552/Analog Input: (RMP--2H [HI], RMP--2J [LO])
Normal aircraft configurations include either two digital or two analog radio altimeter
sources. The T
2
CAS computer unit attempts to establish which type is present in order to
obtain data from one of the two available sources. TCAS first checks the radio altimeter
No. 1 valid flag at RMP--2K. If No. 1 is not valid then No. 2 valid is checked at RBP--3C.
If neither are valid then TCAS checks digital source No. 1 for valid data on the ARINC
429 bus at RMP--13H and RMP--13J. If none of the above are valid then the TCAS
checks the digital source No. 2 for valid data on the ARINC 429 bus at RBP--3D and
RBP--3E. This process is repeated until a valid flag or data is detected.
Until a valid source is found, the TCAS function inhibits all surveillance, CAS, and TA/RA
display functions, records failures in maintenance memory, and sets the TCAS system
status discrete output at RMP--13K to invalid. The TCAS function uses radio altitude to
inhibit advisories and aural annunciation when in close proximity to the ground. This
analog input No. 1, as well as analog input No. 2, can accept data as a dc voltage from
several types of radio altimeters. The type of radio altimeter is selected using the
program pins RMP--12B and RMP--12H thru RMP--12K.
RMP--2K Radio Altimeter No. 1 Valid Input (PO)
See RMP--2H. A valid condition is greater than +18.5 Vdc. An invalid is open circuit.
RMP--3A Corrective Visual Advisory Discrete Output (NO)
The visual advisory discrete outputs are ground/open type discretes (Note 3) used to
operate the annunciator lights on the displays. This output is activated whenever a
corrective aural advisory is issued. The output remains active for the duration of the
advisory unless cancelled by the cancel discrete at RMP--3D. Only one visual advisory is
active at a time. The active state is ground and the inactive state is open.
RMP--3B Preventive Visual Advisory Discrete Output (NO)
Same as RMP--3A, except this discrete is activated whenever a preventative aural
advisory is issued.
RMP--3C Traffic Visual Advisory Discrete Output (NO)
Same as RMP--3A, except this discrete is active during a traf fic advisory.
RMP--3D Cancel Discrete Input (NO)
This input discrete provides a means of canceling aural and visual alerts. It should be
connected to a cancel button (momentary ground type), if used. Groundprox/Windshear
has priority over the cancel button. Open is the inactive state and a momentary ground
(less than 50 Ohms) produces the active state, canceling any active aural or visual alert.