3M C960, Service Information

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Model C960 Headset Intercom System
Operation and Diagrams
1-6
E
3M 2000 May
Base Station
n
Note
Receiver/transmitter and logic circuitry contained
in the C960 headset intercom base station is both
proprietary and non-field repairable. For this
reason, the accompanying base station diagram
provides no circuit component detail. Only those
details that assist fault isolation (such as
connections, configuration jumpers, audio control
circuits, replaceable components and input/output
functions) are shown.
DC Power
DC power for the base station circuits and external
components is provided as follows:
A self-contained DC power transformer, connected to
120VAC, provides unreg12VDC to the base
station power input jack. The +12VDC is turned on
or off by a slide switch located on the front of the base
station. The unregDC is routed through a
protective polyswitch (circuit breaker) to circuit
components and a voltage regulator (called power
supply in the diagram). If an overcurrent condition
causes the polyswitch to open, it automatically resets
after power is removed.
The unreg12VDC is used by the vehicle
detector to provide a +DC vehicle detect signal to the
base station vehicle detect circuits. If an interconnect
module is used in the system, unregDC is
provided to energize the interconnect module relays.
Talk/Page Input
Talkandpagevoicecommunicationstransmittedfrom
the headset are received along with their
accompanying “talk” or “page” control tones.
Received talk communications are routed by the
RCVR & RCVR LOGIC as follows:
S
To the menu sign speaker amplifier via the
DAY/NIGHT volume controls and DAY/NIGHT
switch, through the amplifier to the menu sign
S
To the monitor speaker amplifier via the MON
TALK volume control, through the amplifier and
the Master Monitor Volume control to the monitor
speaker
S
Through the transmit amplifier to the TXMT &
TXMT LOGIC for transmission to all headset
receivers and to output connector pin 9 for use in
cross-lane applications
Received page communications are routed by the
RCVR & RCVR LOGIC as follows:
S
To the monitor speaker amplifier via the MON
PAGE volume control, through the amplifier and
the Master Monitor Volume control to the monitor
speaker
S
Through the transmit amplifier to the TXMT &
TXMT LOGIC for transmission to all headset
receivers, and to output connector pin 9 for use in
cross-lane applications
Vehicle Detector Input
Upon detection of a vehicle, the vehicle detector
signal will be a steady DC or a short-duration DC
pulse depending on whether the vehicle detector is a
“presence” or “pulse” type detector. Upon receipt of
the vehicle detect signal, the VEHICLE DETECT
LOGIC circuit emits alert tones. These alert tones are
routed as follows:
S
To the monitor speaker amplifier via the MON
ALERT volume control, through the monitor
speaker amplifier and the Master Monitor volume
control to the monitor speaker
S
To the transmit amplifier via the Headset Alert
Level control, through the amplifier to the TXMT
& TXMT LOGIC for transmission to all headset
receivers
S
To output connector pin 12 for use in cross-lane
applications