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78793B page 1 of 4
Description
TATTLETALE
®
annunciators and Magnetic Switches are
the nerve centers that translate SWICHGAGE
®
contact
operations into decisions and operate the alarm or
shutdown device. They are the electrical load carrying
devices for the alarm or shutdown device. TATTLETALE
®
annunciators indicate which monitored function failed
leading to the alarm or shutdown whereas magnetic
switches do not. Magnetic switches operate basically as a
latching relay.
Application
Magnetic Switches and TATTLETALE
®
annunciators are
available for use with engines or electric motors. Various
circuits, time delays, and contact configurations are
available to match the power source and mode of
operation required for alarm only, alarm before shutdown
or shutdown only.
For distributor ignition engines, the magnetic switch opens
the distributor coil circuit to cause shutdown. For magneto
or CD ignitions the magnetic switch grounds the ignition
output. Some models can also trip fuel valves instead of
or in addition to grounding the ignition. Diesel engines are
shut down by either closing off the fuel or air supply.
Magnetic switches and TATTLETALE
®
annunciators can
make or break circuits for these engines.
For electric motor applications, various magnetic switches
are available to operate the motor starter, holding coil
directly or in conjunction with appropriate Murphy
Transformer-Relay assembly.
Features
Magnetic switches and TATTLETALE
®
annunciators
described in this bulletin are electrically tripped relay type
devices. Models are available to operate from battery
power, 120 VAC, conventional magnetos and capacitor
discharge type ignitions. Energized to run models allow
CLOSED LOOP circuitry. Others draw momentary power to
trip. Configurations are available for contact make or
contact break to cause shutdown. Some models have both
make and break contacts.
All models have a weather resistant case with screw
terminals for ease of customer hookup. Manually reset
models have a face mounted reset push button which also
serves as a fault indicator in the TATTLETALE
®
version. In
this application, one or more TATTLETALE
®
/magnetic
switches are used to advise operating personnel which
monitored function caused shutdown. Only the
TATTLETALE
®
connected to that function sensor trips
causing the reset push button to pop out.
Electrically reset models perform the same functions as
the manually reset models and are reset by cycling the
power supply off and then on.
Time delay models use reliable solid state timing circuits to
lockout operated switch contacts for start-up and/or to allow
operation of alarms before shutdown occurs. Specific
models allow application of power to a shutdown circuit and
automatic disconnect of power after a given time delay.
See the chart on page 2 for features by part number.
■■
Nerve Centers
for Murphy
SWICHGAGE
®
Instruments and
Automation
Systems
* Applies to selected models.
*
78793B
Revised 4-08
Catalog Section 25
TATTLETALE
®
Annunciators and
Magnetic Switches