The Capacity Operated Relay is a device that can be used as an electronic switch to activate a variety of things. The novel part of the device is that it is operated by a hand approaching or moving away from an antenna attached to the device without actually touching it. In the middle part of the last Century J. W. Miller Co. designed the Capacity Operated Relay and marketed the Miller Cat #695 Capacity Relay Coil so that the device could be manufactured. These devices were used in animated store window displays such that when a window shopper approached and placed their hand near the antenna it activated the window display. They were also used as burglar alarms. My version of the Capacity Operated Relay will switch 120 Volt appliances (lamps, motors, etc.) on and off when the hand is placed close to the antenna plate. It is a project that has a variety of uses both fun and practical and I learned a lot about electronics and tube systems.
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The Miller #695 Capacity Relay Coil

Here is a sample of Tubular Electronics article topics that are planned for the future.

• The Capacity Operated Relay – A lesser known “Weird Science” project that works like magic.

• Upgrade your Hafler DH120 amplifier – This 25-year-old amplifier gets an audiophile overhaul

• Troubleshoot and repair LED Christmas light strings – Find out why they fail so often

• Build a Showman Bass amp head – Modeled after a Fender Dual Showman
  Teaser Pictures:
  Layout of main component board
  Layout of power supply capacitor board
  

• Explore vintage un-built electronic kits in detail – Enjoy the nostalgia of these kits without buying them and paying big bucks on eBay.  See two short “teaser” articles below.

• Build the WaveWizard™ – A high performance Capacity Operated Relay
  Teaser Pictures:
  Layout of oscillator for WaveWizard™ model VT-70
  

• Explore the CCFL (Cold Cathode Fluorescent) lamp – A dimmable energy-efficient light bulb based on good old neon technology

• Restore a Zenith AM radio console

Editor’s Notes:

This is a construction project for a “Capacitance Operated Relay” (a.k.a Capacity Operated Relay) from the “Electronic Hobbyists’ Handbook” by Rufus P. Turner, first published in 1958. (Library of Congress Catalog Card No. 57-9010)

(Information obtained from the United States Copyright Office indicates this book  is no longer under copyright.)

I have added some notes on the construction of this project after the end of the original piece.

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Intermediate Frequency (IF) Tracking Error

Equal Value Superhet Tuning Capacitor Tracking Calculator

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Heath XR-1L after assembly

Photos of an unbuilt Heathkit XR-1 six-transistor radio from around 1958.

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Philmore TR22A after assembly

The Philmore TR22 radio kit from about 1958.

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