3M Food Services Trade Department
3M Center
St. Paul, MN 55144-1000 © 3M 2001 20010214
Intercom Systems
Accessories
Technical Bulletin 2/14/01
New Heavy Duty Handset with Magnetic Switches
A new Heavy Duty Handset with sealed magnetic cradle switches (78-8117-4029-5) will replace the
previous Heavy Duty Handset with open-contact cradle switches (78-6911-2379-4). It is pin-for-pin and
mounting size compatible with the previous models of Heavy Duty Handsets. Very little has changed
except for the cradle switches. See Figure 1.
Advantages:
• Increased cradle switch reliability
• Smaller profile increases interior workspace for wire connections
Notes:
• Cradle switches S1, S2 are shown with the handset off-hook.
• Note polarity of Call Switch connections to intercom.
• If outbound volume to the handset needs to be adjusted in relation to a separate outside speaker,
change the resistor value between terminals 8A and 9A.
• To provide compatibility with C5000 8 Station Controllers starting with serial number 5108001690
and C5000 16 Station Controllers starting with serial number 5116001308, replace the existing
capacitor and resistor connected from handset terminals 6B to 5B with a length of wire.
• When connecting a single wire to a terminal strip, which is 22 gauge or less, strip 1/2" of insulation
and fold the bare wire over double before inserting. When connecting more than one wire to a
terminal strip, twist them together first, apply a small amount of solder, and then insert them into the
terminal strip.
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