AT&T 75 Wiring Manual page 532

66-TYPE HARDWARE
Requirements—Optional DID Make-Busy Trunk
Figure 4-71 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 A25B cable from the emergency transfer unit to a connecting block in the
yellow Trunk/Auxiliary Field associated emergency transfer.
Installation—Terminals
Trunk/Auxiliary Field Connections—Terminals Used Only for Emergency Failure Tansfer
1. At Trunk/Auxiliary Field, run and connect pair of wires between PWR terminals
on yellow emergency transfer connecting block to EM TRANS RELAY PWR (see
Figure 4-69).
2. Run and connect CO trunk circuit leads from the purple field to TC terminals on
the yellow emergency transfer connecting block for each trunk.
3. Run and connect CO trunk circuit leads from the green field to TK terminals on
the yellow emergency transfer connecting block 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 the terminal appearance in the yellow field to the 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 connecting block. Loop the wires from the first appearance to the
last if enough ground terminals are not available (see Figure 4-72).
4-106