Bell System Practices 853AM Identification, Installation, Connections, And Maintenance page 3

ISS 1, SECTION S03-603-130
Fig. 4-Removing Terminal Board Mounting Screw
that options are installed before the telephone set
is connected. To expose the mounting holes, the
hinged chassis assembly must be lowered by
loosening the captive screws (Fig. 3) holding the
top of the chassis. For ease of installation the
chassis assembly can be removed from the base
pan by springing the hinged brackets sufficiently
to clear the pins. The base pan can be mounted
directly to the wall using the keyhole slots, or
holes provided for mounting over an electrical outlet
box.
Warning: Avoid damage to wall or
telephone set whenever chassis is in
lowered position.
The 853AM and 2853AM telephone sets
are factory wired for two intercom
lines only; for the third intercom line
refer to (Fig. 5 and 6).
3.03 The first three pickup positions are arranged
for intercom use only. RED button position
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