3M c960 Service Information page 18

Model C960 Headset Intercom System
Interconnect Module
An interconnect module is needed when a C960
Headset Intercom system includes an auxiliary
intercom to providecontinued communicationswhen
the primary intercom needs service.
The auxiliary intercom may be a conventional,
hard-wired intercom or it may be a second C960 base
station.
External system components (speakers, microphone,
vehicle detector) connect to interconnect module
connector J302. Base station inputs and outputs
(power, common, menu mic, menu speaker, vehicle
detector) connect to interconnect module connector
J303. Auxiliary intercom (or second base station)
inputs and outputs connect to interconnect module
connector J301.
On/Off DC
In the interconnect module schematic diagram, the
interconnect module is shown in its "on" state, with
relays energized.
On/Off control of the interconnectmodule isprovided
by (the presence or absence of) +12VDC from the
(primary) base station. With base station +12VDC
present (via J303 pins 1 and 2), relays K301, K302
and K303energizeto switchmicrophone, speakerand
vehicle detect signals to/from the base station. If the
base station-provided DC is not present (base station
turned off), relays K301, K302 and K303 de-energize
to the switch the same signals to/from the auxiliary
intercom.
Menu Microphone Signal Control
Relay contacts K301-A and K301-B control
distribution of the menu mic signal(s). With relay
K301 energized, the menu mic is connected to the
base station inputs. With Relay K301 de-energized,
the menu mic is connected to the auxiliary intercom.
E 3M 2000 May
OperationandDiagrams
Menu Speaker Audio Control
Relay contacts K302-A and K302-B control
distribution of the menu speaker audio. With relay
K302 energized, the menu speaker is connected tothe
base station. With relay K302 de-energized, themenu
speaker is connected to the auxiliary intercom.
Monitor Speaker Audio Control
RelaycontactsK303-B controldistribution ofmonitor
speaker audio. With relay K303 energized, the drive
side of the monitor speaker is connected to the
monitor speaker output of the base station. With relay
K303 de-energized, the drive side of the monitor
speaker is connected to the monitor speaker output of
the auxiliary intercom. Monitor speaker common is
not switched.
Vehicle Detector Signal DC
While the vehicle detector is powered separately (if it
is a "presence" type detector), vehicle detector signal
DC is always provided by both the base station and
the auxiliary intercom. This vehicle detector signal
DC is available at interconnect module connector
J302-9.
A vehicle detector signal DC of +12VDC is provided
by the base station at J303 pins 9 and 10. A vehicle
detector signal DC of +18VDC is provided by the
auxiliary intercom at J301 pins 1 and 7.
If both the auxiliary intercom and the base station are
ON, the vehicle detector signal will always be
+18VDC because the auxiliary intercom's +18VDC
will take precedence over the +12VDC supplied by
the base station. (Isolation of the two DC sources is
provided by interconnect module diodes D301 and
D303.) If only the base station is ON, the vehicle
detector signal DC will be +12VDC.
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