\
NPE O
NPE 1
●
❘
PORT
T.3
❘
❘
●
ON-BOARD
MICROPROCESSOR
PORT
1/0
CIRCUIT
●
●PORT
●
CIRCUIT
●4
R.4
GROUND
DETECTOR
PORT
CIRCUIT
0
CODEC
HYBRID
T.O
R.O
CIRCUIT
3
R.3
T.4
TO
CENTRAL
OFFICE
●❘
❘
❘
T.7
PORT
CIRCUIT
7
R.7
/
Figure 3-8. Unique Ground Start Trunk (ZTN76) Circuitry3-17