(5) The two lamp signals immediately in front of each pair of cords are the supervisory signals associated with
these cords. The supervisory signal farthest from the operator is the A cord signal. The signal nearer the operator is the C
cord signal. These signals inform the operator when one or another of the connected stations hangs up the receiver, or
whether either station jiggles the hookswitch. The supervisory signals are discussed in more detail in later paragraphs.
(6) The switch levers shown on the switchshelf control the associated listening and ringing switches. Each pair
of switches is associated with a pair of adjacent cords. Each switch lever may be placed in any one of the following
positions: In any selected pair of levers, the lever farthest from the operator, when drawn backward toward the operator,
operates the associated switch, which connects ringing power to the ring and tip of the A cord. Pushing the lever away
from the operator establishes in the associated cord circuit a condition commonly referred to as a night connection. When
the lever is vertical, the associated switch is in its neutral position. The lever nearer the operator, when moved away from
the operator, connects the operator's telephone set to that particular cord circuit, permitting intercommunication among the
operator and the stations connected by the cord circuit. When the lever is drawn toward the operator, ringing power is
connected to the ring and tip of the C cord. Service at a switchboard sometimes requires that certain extension stations be
connected to central-office lines during times while the switchboard is unattended, such as outside of regular business
hours, and at night. This service can be provided in the usual manner by connecting the A cord to the extension station
and the C cord to the central-office line. The act of connecting the C cord to the central-office line, however,
automatically connects a bridge across the ring and tip cord conductors, and thus a signal appears at the central-office
switchboard, even when the receiver is on the hookswitch at the extension station. The undesirable condition is corrected
when the night-connection switch is moved to the operated position. This operation opens the bridge across the ring and
the tip cord conductors and holds the central-office line open until the receiver is removed from the hookswitch at the
extension station. This establishes the night connection.
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