TM 55-1930-209-14&P-12
APPLICATION NOTE
MODELS M3115 and M3116
POWER CONTROL MODULES
(Formerly Models 3PC-12 and 3PC-24)
INTRODUCTION
The M3115 and M3116 are modules which allow David Clark Company Incorporated intercom systems to be
powered by external batteries or by an external DC power source when a M3111 power supply is not used. The
M3115 uses a 12-14 volt source, and the M3116 uses a 24-26 volt source.
PHYSICAL CHARACTERISTICS
The M3115 and M3116 modules are designed to fit into a standard electrical wiring box that is at least 1-3/4 inches
deep. They each occupy one 'space', or the equivalent of one duplex outlet, and may be covered with any duplex
outlet cover. Any number of modules may be nested together using a multiple gang box.
The M3115 and M3116 may also be mounted in a panel by drilling clearance holes for the fuseholder, the shank of
the illuminated switch, and a 6-32 screw. The module is held against the back of the panel by the 6-32 that
normally holds the cover plate on, and by the nut on the switch shank.
The rear of the M3115 and M3116 contain an 8-terminal strip which gives access to the circuitry. The easiest
crimp terminal to use is an insulated, slotted-tongue flanged spade such as the AMP P/N 324608 or an equivalent.
ELECTRICAL CHARACTERISTICS
The M3115 operates from a 12 to 14 volt battery or DC power source. The indicator lamp provided is a No. 336,
which draws 0.08 amps at 14 volts. The output of the M3115 is protected by a 1/2 amp slow blow fuse, type MDA-
1/2, and the power switch is a push on/push off type that lights up when the system is on. A M3115 will operate a
David Clark Company intercom normally, with two exceptions. First, the only headset station that will run on 12
volts is the-M3145, and ten of these may be used, provided that each headset has a push-to-talk switch. The other
exception is that the maximum obtainable audio level at the headset will be half (6 dB less) of what it would be if
the system were run on 24 volts.
The M3116 operates from a 24 to 26 volt battery or DC power source. If a 24 volt battery is used which has a
charging facility connected to it, care must be taken that the voltage never goes above 26 volts at any time. The
battery charger must be disconnected while the intercom system is running if the voltage could go over 26 volts.
The M3116 comes with a No. 334 indicator lamp, which draws 0.04 amps at 28 volts. The output is protected by a
1/2 amp slow blow fuse, type MDA-1/2, and the power switch is the same push-on/push-off type used on the
M3115. All David Clark Company intercom system modules will operate normally from the M3116, with no
changes required. A M3116 plus external 24 volt DC source Is directly interchangeable with the A.C. operated
M3111 power supply.
17206P-27 (Rev. June, 1976) Page 1 of 2
