Vibrator or Chopper, Hughes-Airpax, lot of 20 units.

http://us.ebid.net/for-sale/vibrator...pax-lot-of-20-
units-139316949.htm

This is a plug-in chopper (or vibrator): mil-spec, unused old surplus,
but may be a bit scratched up. It is in sealed metal can about the size
of a mini tube and plug into a 7-pin mini tube socket. It has a coil and
a SPDT contact which will close with just a few volts on the coil. Made
by Hughes, p/n 992200-1, Airpax C-747. Equivalent to Oak Chopper type
610, and Collins 54-1021-00. Size is 3/4" dia x 1-3/4" long, weight 1
ounce. A previous buyer said these were used on older military radios
like the ARC-38. Some of the units are also marked "400 Hz". I also
have this in a lot of 3.