The "SCRED" R&D Prototype Survey Meter (ca. 1965-1970)


The "SCRED," produced in the early 1970s by Thermo Electron Engineering Corporation of Waltham Massachusetts, was the prototype for a proposed civil defense meter. As might be expected, SCRED is an acronym: it stands for Secondary Compton Recoil Electron Detector. The interesting thing about the unit is that it does not employ batteries. It was powered by the Compton scattered electrons produced by the exposures to X-rays and gamma rays. At least I think that was supposed to be the idea.

Alas, this example does not appear to be in working condition. 

The sensing element is a heavy metal cased cylinder (ca. 3” in diameter and 3.25” long) located in the rear bottom of the case.


It has three controls: a range switch, button activating a magnetic switch (to the left of the meter) and an unmarked potentiometer.

The Scred detector is described briefly in the 1966 List of Military and Civil Defense Devices as: "A Solid Compton Recoil Electron Detector as a battery-less dose rate measuring device for gamma radiation measurement."

Range: 0-5, 0-50, 0-500, 0-5000 R/h

Size: 4.25” x 8” x 3.25”

Donated by the Federal Emergency Management Agency courtesy of Carl Siebentritt.


  • Carl Siebentritt, personal communication.
  • Defense Atomic Support Agency List of Military and Civil Defense Devices DASA 1243 revised, 1966.