[ARC5] Weird headphones.

[Michael A. Bittner]

Ken,

The PRD-1 is an Army direction finder.  It has a 600 Ohm audio output for phones.  The typical designation for radiation detectors is PDR.. Easy to confuse the two.  

Mike Bittner, W6MAB

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  ----- Original Message ----- 
  From: Kenneth G. Gordon 
  To: ARC5 
  Sent: Tuesday, July 01, 2014 11:44 AM
  Subject: [ARC5] Weird headphones.


  Hello again, Gents:

  I have been using a set of headphones for the past several years that 
  have always intrigued me.

  The outsides are a thin bakelite, tear-drop shaped housing with nice semi-
  hard rubber pads fitted over them.

  Inside of each ear-piece is an element with the following marks on them:

  ANB-H-1A, then in paint PRD1

  The headband is engraved HB-7, appears to be made of stainless steel, and 
  has leather coverings over the two adjustable spring "loops".

  When I found them in my junque, they were missing the cords, so I wired 
  them in series, properly phasing them in the process.

  They have always worked well for me, although I do have to replace the 
  cords periodically since the wire I use is thin and easily broken.

  My questions are 1) what is the likely impedance of these (I have assumed 
  600 ohms), 2) doesn't the PRD1 indicate that they were probably used with 
  either a radiation meter of some sort or perhaps a mine-detector. 3) how 
  old might they be?

  I have never seen a set of military headphones with tear-drop shaped 
  housings before.

  Ken W7EKB
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