User's Manual

1.3.2.8.1 Interface CCA Detailed Theory
The Interface CCA provides interface connections between the Backplane CCA and the outside world. All
signals are protected by transient voltage suppression (TVS) devices. All connections between the Interface
CCA and the Backplane CCA are accomplished via headers J1 and J2. The J2 and J3 connections will not
be used in a DME system since there will not be a TACAN antenna system controller.
On-board sensor U1 provides interior (cabinet) temperature while an exterior sensor can be interfaced via
RJ11 connector J7. Interior temperature sensor U1 is TVS-protected by diode CR68 while the exterior
temperature signal is protected by diode CR29. Earth or chassis ground is connected by lug E1 and inductor
L1. Circuit or analog ground is accessible at test points TP4 and TP5.
The +24VDC power, which originates at the Facilities CCA, is indicated present by LED CR71 and resistor
R30. The +24VDC is TVS-protected by diode CR44 and available to be measured through resistor R28 and
test point TP3. The +24VDC powers the INTERLOCK and EXT_KEY_IN opto-isolators, the optional
Ethernet module J9, and an off-board radio/RF modem via terminal block TB2-9.
Optional Ethernet module J9 has an RJ45 connector, is TVS-protected by U4 through U6, is powered by
DC-DC converter PS1, and has its TTL signals converted to RS232 by U7 before routing eventually to the
RMS CCA. Diodes CR41 through CR43 insure the proper voltage level before entry into PS1. PS1
converts +24VDC to +3.3VDC and diode CR72 provide TVS protection.
All TACAN antenna system controller signals are TVS-protected by diodes CR45 through CR67 before
routed to DB37 connector J3.
Test header J8 is used for factory testing.
The RCSU has two possible paths for communications; either tip-n-ring to terminal block TB2-1 and TB2-
2 or RS232 to DB9 connector J5. The active path is configured by a system configuration DIP switch on
the Low Power Backplane CCA. Diodes CR21 through CR24 provide TVS protection for the RS232
signals while resistors R21 through R24, spark-gap V2, sidactor Q3, and balun L2 provide the TVS
protection for the tip and ring signals.
The PMDT also has two possible paths for communications; either tip-n-ring to terminal block TB2-3 and
TB2-4 or RS232 to DB9 connector J6. The active path is configured by a system configuration DIP switch
on the Low Power Backplane CCA. Diodes CR25 through CR28 provide TVS protection for the RS232
signals while resistors R17 through R20, spark-gap V1, sidactor Q2, and balun L3 provide the TVS
protection for the tip and ring signals.
Spare I/O terminal block TB1 provides connection to ten spare analog inputs, four spare digital outputs,
and four spare digital inputs. All of these signals are TVS-protected by diodes CR1 through CR18. All of
these signals eventually route to the Facilities CCA.
External interconnect terminal block TB2 provides connection for the remainder of the signals of the
Interface CCA. The SMOKE_DETECTOR and INTRUSION_SENSOR signals are TVS-protected by
diodes CR37 and CR38. The ILS-VOR RS-232 signals are TVS-protected by diodes CR19 and CR20.
The INTERLOCK+ and INTERLOCK- signals are connected to opto-coupler U3:A. Full power supply
isolation can be achieved by removing jumpers JP1A and JP1B from header JP1 if the customer is willing
to provide an external supply. Current is set and steered through the LED of U3:A by resistors R14 through
R15 and diodes CR36 and CR69. The transistor output of U3:A is TVS-protected by diode CR39.
The EXT_KEY_IN+ and EXT_KEY_IN- signals are connected to opto-coupler U3:B. Full power supply
isolation can be achieved by removing jumpers JP2A and JP2B from header JP2 if the customer is willing
to provide an external supply. Current is set and steered through the LED of U3:B by resistors R5 through
R7 and diodes CR32 and CR70. The transistor output of U3:B is TVS-protected by diode CR40.