AT&T 75 Wiring Manual page 361

Requirements—Optional DID Make-Busy Trunk
Figure 3-109 shows the connections at the Trunk/Auxiliary Field for an optional Direct
Inward Dialing (DID) make-busy trunk. This option prevents DID trunks from being taken
out of service by the serving central office during emergency transfer. This trunk is used for
this function only and should be specified to appear on the twenty-fifth pair of a network
interface jack.
Installation—Emergency Transfer Units
1. Mount emergency transfer unit on the wall to the left of the Trunk/Auxiliary
Field. Additional units should be mounted below the first one in a column.
2. Connect B25A cable from the emergency transfer unit to a connector associated
with the yellow emergency transfer row in the Trunk/Auxiliary Field.
Installation—Terminals
Trunk/Auxiliary Field Connections—Terminals Used Only for Emergency Failure Transfer
1. At Trunk/Auxiliary Field, run and connect pair of wires between PWR terminals
on yellow emergency transfer row to EM TRANS RELAY PWR (see Figure 3-107).
2. Run and connect CO trunk circuit leads from the purple field to TC terminals on
the yellow emergency transfer row for each trunk.
3. Run and connect CO trunk circuit leads from the green field to TK terminals on
the yellow emergency transfer row for each trunk.
4. Connect the ST terminal leads on the yellow emergency transfer row for each
emergency transfer terminal to the terminal appearance in the yellow
Trunk/Auxiliary Field (see Note).
Note: The ST terminal leads should be terminated on the following pairs 1,
4, 7, 10, 13, 16, 19, or 22 (the first pair of any 3-pair group).
5. Connect this row to blue or white station distribution field.
6. If ground start must be provided, run and connect two wires from ground
terminals to the third pair for each emergency terminal appearance on the yellow
Trunk/Auxiliary row created in step 4. Loop the wires from the first appearance
to the last if enough ground terminals are not available (see Figure 3-110).
110-TYPE HARDWARE
3-145