AT&T Network Adapter 25 Installation And Maintenance Manual page 74

INSTALLATION
Tie trunks must be segregated on a separate block because a different
splitter cable is used. Also, off-premises stations must be segregated one
700A Jack.
The first five trunks in each group of eight (loop start or ground start trunks
only) can be connected through an ETU to five power failure transfer stations.
However, all eight trunks are connected to, and pass through, the ETU.
The ETU also supports a DID make-busy function to the central office's extra
pair (if required). Relay contacts for the DID make-busy function appear on
the 25th pair on the TAE block. The relay contacts are normally open. When
power fails, the contacts close, making all DID trunks appear busy to the
central office. This prevents the central office from taking the DID trunks out
of service.
A maximum of four ETUs are supported. For a system with more than one
ETU, apportion the emergency transfer trunks so that they are in the first
subgroup of five in each subgroup of eight trunks on a connecting block.
1. Connect an A25D 25-pair single-ended cable to each network
interface receptacle.
2. Cut down the other end of each cable on the top terminal row of a
700A Jack in groups of eight trunks (four for tie trunks), as described
above (see Note). Cut down the DID make-busy pair (if provided) to
terminals 49 and 50 on the block.
Facilities used for off-premises stations, must be
Note:
segregated on one 700A Jack.
3. Install secondary wiring protectors (sneak current fuses) between the
bottom terminal rows on the 700A Jacks for each trunk cut down on
the top row. (Approved protectors are listed in Table 2-B, along with
their respective CPs.)
2-50