The pinlayouts for all the 308 models is the same.
PC -> PABX
2 -> 3
3 -> 2
4 -> 6
5 -> 5
6 -> 4
7 -> 8
8 -> 7
Please note: This pinouts is also used for the Panasonic TDA30.
Pinouts: 9 pin
PABX -> TNG Buffer:
3 - 2
4 -
| strapped
6 -
5 (O Volts) - 5