Emergency Transfer Units - AT&T System 75 Wiring Diagram

Emergency Transfer Units

General
The emergency transfer units used with the 66-type/110-type hardware
are the Z1A emergency transfer unit and the 574-5 power transfer unit.
The units mount on the plywood backboard to the left of the
trunk/auxiliary field.
Z1A Emergency Transfer Unit
The Z1A emergency transfer unit provides emergency transfer
connections for six telephones. If the central office (CO) trunks require
ground start, a ground start key must be installed on each emergency
transfer telephone.
574-5 Power Transfer Unit
The 574-5 power transfer unit (Figure 2-19) provides power transfer
connections for five telephones. This unit provides automatic ground
start.
Associated Hardware
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