Mitel SX-200 Documentation page 719

SECTION MITL91 OS/91 lo-096-500-NA
0
Power fail transfer control switches
c
0
Status LEDs on most cards
0
Busy switches and LEDs on trunk cards
0
Fault readout on the console
0
Test line
0
Console clock
4.02 The system maintenance philosophy assumes that faulty print-
ed circuit cards or assemblies are replaced in the field and the
faulty items are returned to MlTEL for repair.
B. Power-Up Diagnostics
4.03 Each time power is applied to the system, the Power-Up Diag-
nostics check the Random Access Memory (RAM), the Program-
mable Read Only Memory (PROM) and the Non-Volatile Random Ac-
cess Memory. The RAM is checked by setting all bits to 1, then to 0,
and a check is performed to ensure that each bit is set correctly. If an
error is detected, a major alarm is raised. The PROM check consists of
compiling a checksum of all the PROM bits and comparing the result
with the checksum produced when the PROM was manufactured. A
difference in the two checksums will result in a major alarm. The
Non-Volatile RAM check consists of compiling a checksum of all the
bits in the Non-Volatile RAM and comparing this with the checksum
generated when the Non-Volatile RAM was last programmed. A dif-
ference in the checksums will result in a minor alarm.
4.04 During the power-up sequence, the scanner operation is also
checked. tf a malfunction is detected, a major alarm is raised. If
the system powers up correctly, the console clock displays 00.00 and
starts to run.
C. Automatic Diagnostics
4.05 The Automatic Diagnostics test the speech path connections,
tone and rotary receivers, tone and rotary generators, supervi-
sory tones and speech path biasing. The automatic diagnostics run at
all times except when there are four or less speech paths free in the
system, or when a console is in the programming mode. The diag-
nostics will not use a receiver if any other equipment is waiting for a
receiver.
4.06 Faults found are reported as minor alarms and the failing unit is
busied-out, if possible. The automatic diagnostics will not busy
out more than haff the receivers, generators,-or speech paths, to guard c
against the possibility that an error in the fault detection circuitry
could shut down the system.
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