Mitel SX-200 Documentation page 467

Superswitch electronic private automatic branch exchange epabx

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SECTION 91 OS/91 1 O-096-180-NA

Each speech path (including the "Music on Hold" speech path) is

directly wired on each line, trunk, tone, receiver and console

control circuit card to an 8804 which can, under processor control, be

connected to any circuit on the card (i.e., a line circuit, a tone gener-

ator, etc.). The processor sends a card select (CS) signal to access a

particular card together with a combination of address lines and data

lines which close the required "contact". The concept discussed in the

foregoing description is illustrated in Figure 8-l.

The following subparagraphs detail the sequence of circuit op-

erations encountered within the PBX system during the pro-

gress of calls.

Figure 8-2 and Table 8-l should be consulted when reading the

descriptive material. In addition, the following abbreviations

have the meanings indicated in the text:

calls (DTMF - type only) to dial PBX features or exten-

sions directly

"loop-start" (LS) facility

Off-Hook (Extension)

When an extension goes off-hook, drawing loop current, the

fact is detected by an op-amp which turns on a LED on the line

circuit card and sets a signal, OFF-HOOK X (where X represents. one of

the eight lines on the PCB), which is fed to an analog switch together

with a similar signal for each of the other seven lines. When the ,::$I

scanner addresses each of these lines via the IA bus, the OFF-HOOK X

state is presented on the IZ line for that particular line circuit card.

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