User's Manual

U31 and U32 buffer the power OK signals of up to seven Amplifier CCAs, two Monitor CCAs, and two
Receiver/Transmitter Controller CCAs as well as the A-D status signal, the INTERLOCK signal, the
~FANS_OK signal, the SMOKE_DETECTOR signal, and the INTRUSION_SENSOR signal. All of these
signals originate at various cards in the Low Power and High Power Backplanes except the last four
signals, which originate at the Interface CCA.
The U18 buffer reads the frequency select switches, which reside on the Low Power Backplane CCA and
determine the operating frequency of the DME system.
The U37 buffer reads TTL signals which originate at the TACAN antenna system controller, routed
through the Interface CCA, and converted from RS422 by U34. The U38 output latch allows the RMS
CCA to direct activity of the TACAN antenna system controller after the latch TTL signals are converted to
RS422 by U35 and U36. The U38 loop-back signal may be used for fault-isolation purposes to buffer U37.
The U22 latch controls the 32 channels of analog signals through multiplexers U20 and U21 as well as A-D
convert/address and PWR_OK indicator. The U23 latch provides the spare digital outputs of the Interface
CCA after buffering by U24 as well as the Ident tone multiplexer control and the fans on/off signal through
transistor Q2.
Test header J1 is used for factory testing only.