First Option:
Pins:
1 spare
2 TX
3 RX
4 DSR
5 GROUND
6 DTR
Connections PABX -> PC:
2 & 2
3 & 3 (Variation: swop 2 and 3)
5 & 5
4 & 6
2400 baud rate
2nd Option:
9 pin:
PC -> PABX
2 -> 2
5 -> 5
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| 4 (4 & 6 STRAP ON PABX SYSTEM SIDE)
| 6
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