66-TYPE HARDWARE
EMERGENCY TRANSFER UNITS
The emergency transfer units used with the 66-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 unit provides emergency transfer connections for six analog voice terminals to six
trunks. If the central office trunks require ground start, a ground start key must be
installed on each emergency transfer voice terminal.
574-5 Power Transfer Unit
The 574-5 unit provides emergency transfer connections for five analog voice terminals to
five trunks. This unit provides automatic ground start.
TRUNK CONCENTRATOR CABLES
Trunk concentrator cables are used for the following purposes:
●
Match 1-pair local telephone company trunks to 3-pair circuits that connect to the
switch.
● Match 1-pair local telephone company trunks provided for off-premises lines to 3-pair
circuits that connect to the cross-connect field.
●
Split eight 3-pair analog tie trunks into two groups of four 3-pair tie trunks that
connect to the switch
The trunk concentrator cables are 25 feet (7.6 m) in length. They are coded as cable
assemblies and are available as described below.
WP-90929, List 2, Cable Assembly
The WP-90929, List 2, Cable Assembly (Figure 4-9 and Table 4-B) is used to connect local
telephone company trunks to the system switch. It is also used to connect off-premise
analog circuits from the port field to the trunk field in the equipment room cross-connect
field. The 3-fingered end of the cable assembly contains male ribbon connectors; the other
end contains a female ribbon connector. Each cable assembly can match twenty-four 1-pair
trunk circuits to twenty-four 3-pair trunk circuits.
WP-90929, List 4, Cable Assembly
The WP-90929, List 4, Cable Assembly (Figure 4-9 and Table 4-C) is used to connect tie-
trunk circuits to the system switch. The 2-fingered end of the cable assembly contains male
ribbon connectors; the other end contains a female ribbon connector. Each cable assembly
can match eight 3-pair tie-trunk circuits to two groups of four 3-pair tie-trunk circuits.
4-16
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