User's Manual

The tip and ring signals from dedicated modem U14 are isolated, TVS-protected, and filtered by T1, CR8,
FL4, and FL5 before exiting connector P2-A14 and P2-A15. Audio from U14-64 is scaled by R28 and R30
before audio header JP1-3.
Three more sources of audio (other than the modems) are controlled by analog multiplexer U16.
MON1_AUDIO_ID and MON2_AUDIO_ID from P1-C1 and P1-C2 (originally from the Monitor CCAs)
connect to multiplexer U16-15 and U16-12. The third audio source is generated by 1KHz oscillator CR34,
U17:A, C65, and R62 when the ~TEST signal is active. ID_MUX0 and ID_MUX1 (U16-11 and U16-10)
select monitor audio through U16 except when ~TEST is active.
Resistors R39 and R38 scale the monitor or test audio output of U16-3 and feed it to AC-coupling capacitor
C30. Amplifier U15 amplifies the sum of audio presented through R32, R33, and R34 and drives speaker
SPK1 as determined by gain resistor R37. Amplifier U15 (and therefore all audio) is disabled if no jumper
is present between audio header JP1-5 and JP1-6. Each modem’s audio output can be disabled by either
removing jumpers between audio header JP1-1 and JP1-2 or JP1-3 and JP1-4.
The exterior and interior temperature circuitry operate identically. Therefore only the exterior shall be
discussed. The exterior temperature sensor signal (EXTERIOR_TEMP) from P1-A21 is converted from
current to voltage by R41 and R43 before routing to buffer U19-3. The U19-1 buffered output
(EXT_TEMP) is scaled by resistor network RN14-5/12 and RN14-6/11 before connection to the J1 test
header and analog multiplexer U21-26 as ETMP_SCALED.
Test header J1 is used for factory testing only.
All on-board power supplies are scaled and presented to both the J1 test header and analog multiplexers
U20 and U21. These supplies are DVCC (+3.3V), +5DIG, +12DIG, +12ANA, -12DIG, -12ANA, +15V, -
15V, +24V, 1_+48V, and 2_+48V and are scaled by resistor networks RN14, RN4, RN5, RN1, and RN2.
Other signals routed to the analog multiplexers are SPARE_ANA1 through SPARE_ANA10,
SPARE_DIN1 through SPARE_DIN4, +5Vref created by U30, digital ground, and analog ground.
An individual channel of the 32 possible channels for the U20/U21 analog multiplexer pair is selected by
MUX0 through MUX4 from latch U22. Inverter U17:B insures MUX4 enables only U20 or U21. The
enabled U20 or U21 multiplexer passes its signal to buffer U25-3. Buffer output U25-6 passes the signal to
A-D converter U26-14.
The U26 A-D converts the analog input signal to digital data outputs when commanded by latch U22-15.
The end-of-conversion is signaled by U26-28; which is read through buffer U31-9. The digital data outputs
of the A-D are pulled-up by RN6 and buffered through U27 to the data bus.
The system configuration switch signals (SCON0 through SCON15) enter via connector P1, are pulled-up
by resistor networks RN7 and RN8, and then connect to buffers U28 and U29. Channel select inputs
CSEL0 through CSEL7 enter via connector P1, are pulled-up by resistor network RN11, and are buffered
to the data bus by U18.
Power OK signals from the Low Power Amplifiers, High Power Amplifiers, Monitor CCAs, and
Receiver/Transmitter Controllers as well as status signals INTERLOCK and ~FANS_OK connect to
buffers U31 and U32 and resistor networks RN9 and RN10. Resistors R16 and R26 provide a high current
pull-up for SMOKE_DETECTOR and INTRUSION_SENSOR signals before buffer U32.
Latch U23 drives SPARE_DOU1 through SPARE_DOUT4 through buffer U24 to connector P1. Latch
U23-12 drives the FANS_ON signal through inverter U17:C and transistor Q2 to connector P2-B16 while
CR42 provides transient protection. Finally, latch U23 controls audio multiplexer U16 via ID_MUX0 and
ID_MUX1 (discussed previously).
The U37 buffer reads TACAN antenna controller signals which enter through connector P1 and are