of this attendant during
business hours is to answer trunk calls from the main office and finding
out what party is desired, call up the proper station on the
intercommunicating system. The party at that station may then connect
himself with the trunk.

The practice of the Dean Company, for instance, is as follows in regard
to trunking between intercommunicating systems and main offices with
common-battery equipment. The attendant's station telephone cabinet
contains, besides the push-button keys for local and trunk connections,
a drop signal and release key, together with relays in each trunk
circuit. The latter are used to hold the trunks until the desired party
responds.

The main-exchange trunk lines, besides terminating at the attendant's
station, are wired through the complete intercommunicating system so
that any intercommunicating telephone can be connected direct to the
central office by depressing the trunk key, which is provided with a
button of distinctive color. The pressing of the trunk key allows the
telephone to take its current from the main-office storage battery and
to operate the main-office line and supervisory signals direct, without
making it necessary to call on the attendant to set up the connection.

[Illustration: Fig. 450. Junction Box]

[Illustration: Fig. 451. Typical Arrangement of Intercommunicating
System]

Incoming calls from the common-battery main office to the
intercommunicating system are all handled by the attendant. The
main-office operator signals the intercommunicating system by ringing,
the same as for a regular subscriber's line. This will operate a drop in
the attendant's station cabinet, and through an armature contact, give a
signal on a low-pitched buzzer. This alarm buzzer operates only when the
main exchange is ringing and, therefore, does not require that the drop
shutter be restored immediately. An extra key may be provided for an
extension night-alarm bell, for use where the attendant also does work
in a room separate from that containing the attendant's station
telephone equipment.

The attendant operator answers the main-line signal by pressing the
proper trunk button, as designated by the operated drop on the
attendant's cabinet. The answering of the trunk connects a locking relay
across the circuit so that the attendant may call the desired party on
the intercommunicating system without having to hold the trunk manually.
The party desired is then notified