Specifications

151
CPU Card (702-9176)
Station cards. The SELECT light and the TEST 3 lights indicate transactions between the
paging system and the interface cards. It is normal to see the Station cards blink at a faster
rate than the Trunk cards in order to give outgoing paging high priority. It is also normal
that the SELECT light of the Station card farthest to the right in the card cage appears on
most of the time. In fact, it is blinking at the same rate but for a longer period giving the
illusion of being on solid.
Call Processing
The dual (702-9117) Trunk card TEST 1 light indicates decoding of dial pulse, DTMF, or
voice for the first unit or phone line while the TEST 2 light does the same for the second.
The Station card test lights do not generally light. See Trunk Cards and Connections on
page 71, Radio System on page 97, and Troubleshooting and Repair Procedures on page
179 for more information on lights.
CPU Card (702-9176)
Advanced large-scale integrated circuits (LSI) pack an entire computer, including 1MB to
4MB or more of memory. Paging software loaded from hard disk at power-on operates in
the RAM memory on this card and acts as traffic manager and diagnostic maintenance
controller for the microprocessors on all of the telephone and radio interface cards.
This card also provides the central timing logic for the PCM digitized audio highway that
all of the circuit cards use for passing audio among them. Prompting tones are generated
on dedicated PCM channel slots for 1 kHz beep, out of service whoop, telco dial tone,
telco ringing sound, and telco busy sound.
Power-on reset timing and a watchdog circuit help recover from any software faults or
high energy noise interference that might stop system operation. Front panel indicators are
addressable by the CPU to show operating system status.
The CPU provides PCM synchronization pulses, master reset signal, watchdog timer, non-
volatile RAM, a temperature sensor and A/D converter, and a real-time clock.
The watchdog and reset circuit is comprised of U25, and U64. U64 provides the initial 300
millisecond power-up reset pulse. U25 is the watchdog timer. The system must write to it
once a second to keep it from initializing a reset pulse. The watchdog is disabled from
resetting the system for about four minutes from power up so to let the system boot all of
the way up. The watchdog can be disabled by placing switch 7, labeled “WAT ”, in the
“A” position.
The PCM highway is comprised of three signals: data, clock, and sync. Data is a time-
multiplexed serial signal and can be encoded or decoded by almost any Zetron card. The
clock and sync signal is produced on the Master Card.