EM200 Ear Mike
NSN 5965-01-187-3078

Brooke Clarke, N6GCE


General Information

At first look this appears to be an in the ear type of earphone, but it is also a Microphone!  There are two parts:
Ear Piece - with 1 meter (40") long cord & 0.198 O.D. plug (TP-120?) with 4 barbs that positively lock the plug into the socket on the control box.  You must pull back on the plug's outer sleeve and when the sleeve moves back it retracts the barbs, freeing the plug.  You can be sure the earpiece will not unplug!  You "screw" the ear piece into your ear, comfortable and held better than the push in type earphones.
Control Box - with belt hook, PTT switch and "Hi Low" Microphone sensitivity switch.  When in the Hi position you can whisper and easily be heard.  The radio connector is the standard 5-pin U-229.  The cord is 2 feet long.  The PTT switch has a noisy action, you would not want to use it in a quiet environment.  It sounds like a child's "cricket" noise maker.  One of the optional Telex switches would be a better choice.  The company that made this used to be called Magnacom (or Magnum Distribution in Canada) and was later bought by Telex.

There may be two versions of the EM200 on the surplus market, one as shown here is the military version which has the radio cord permanently attached to the control box and the other a commercial version with the "EM200" label and a removable radio cord.

There is an adjustment on the side of the box under a rubber plug, to adjust the microphone taking into account the earmold in use and for the users actual ear.  This is done by placing a receiver six feet away and facing away from the user with the volume set for 1/2 way.  The adjustment is turned until there is feedback and turned the other way until the feedback stops (while transmitting).

Label on Box - FSCM 37695 (Magnavox) p/n 588008-101
Photo from eBay - shown with PRC series Squad Radio.
This is classified as a headset becasue it's head mounted and is the "set" of microphone and earphone.
There is no noise canceling feature.  When using on the "HI" setting with a radio tuned to the output, there will be a squeal because of feedback.  Of all the microphones I have, this is the most sensitive in this regard.
Photo installed in my ear.
The cord from the control box to the ear piece can be unplugged from the ear piece by means of a two pronged plug on the cord.
It's not clear to me how you remove the ear mold in order to replace it with different sizes or left ear molds.

Nice photos from eBay - note that the cable is listed as for the PRC-68B which helps date the EM-200.  This cable will work for almost any mil radio that takes U-229 audio accessories.  This was labeled as made by Magnum Distribution.  Note that this version has the "EM200" label and that the radio cord can be removed from the control box.  NSN 5965-01-187-3078 is the same NSN as the one with the removable radio cord.

Power Source

Internal single 1.5 Volt AA battery.  Although there was not a gasket between the back cover and the box, it looks like one should be there.
Maybe this is available as a spare part?  Without a gasket or using RS Lube Gel, moisture can easily get inside.

Factory Operation Instructions -

Including how to set the gain control.
HI/Normal switch refers to the outside noise level.
Available direct from Telex.


Telex - Land Mobil Radio - EM200 & EM300 Ear Mikes - the EM200 looks identical to this unit.  Proably Magnavox OEMd the EM200 with the U-229 connector. Sales Brochure em-200-300.pdf - the optional PTT switches are also listed

Jabra - has a line of Ear Sets that are ear mikes with a 2.5 mm connector to fit cordless phones, and other models with connectors to fit cell phones.  A review says that they are very sensitive to wind noise.  LAS VEGAS, March 20, 2001 . . . "The updated version has a discreet profile designed to fit closer to the ear and has been re-engineered to improve its resistance to wind noise. The EarSet is available for a suggested retail price of $39.99."  The cordless phone models have more mike gain.  All of these are full duplex, so a PTT would need to be added for use with mil radios.


2122191 Sound translation apparatus, Ballantine Stuart, 1938-06-28, 381/98; 330/150; 333/28T; 381/111; 381/151; 381/180- throat mike
2148477 Bone
                  conduction audiphone, Koch Henry, Dictograph Prod Co,
2148477 Bone conduction audiphone, Koch Henry, Dictograph Prod Co, 1939-02-28, 381/151; 181/400; 381/162; 381/380 -

not really about ear mikes, but is related.
                  Communicating system, William S Halstead, Farnsworth
                  Research Corp, 1950-12-26, -
2535063 Communicating system, William S Halstead, Farnsworth Research Corp, 1950-12-26, 455/83; 343/720; 381/111; 343/718; 367/903; 455/270 -

11 prior art patents

Cited by 43 patents:

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