Radio News Magazine Oct. 1926

This cover from the October, 1926 issue of Radio News shows the "Radio Burglar Alarm" in action. Caught redhanded with his tools on the floor, a would-be safecracker cowers in terror under a spotlight. Atop the safe is a radio which presumably plays some role in bringing the evildoer to justice.

If you go on to read the article, you will learn that "Capacitor Burglar Alarm" might have been a better title. The somewhat far-fetched design relies on the capacitance effect of the human body, and it doesn't involve radio waves at all. Hidden under the carpet beneath the safe is a large metal plate, which extends several feet past the safe in all directions. The plate and the safe are wired together, forming two plates of a giant capacitor. The rest of the circuit consists of a dry cell to supply power, a coil and tube to detect changes in capacitance, and a relay to trigger some kind of alarm device.

When a would-be burglar stands on the metal plate, his body capacitance changes the balance of the circuit, triggering the relay to ring a bell at the police station, set off lights and alarms at the premises, or take some other action. The cover artist exercised a bit of creative license in placing a radio atop the safe. The article doesn't mention radio transmission at all, although possibly the device triggered by the relay could have been a transmitter beaming some signal to a waiting receiver.

This novel idea was not very practical, given the limitations of 1920s technology. However, the basic concept was realized decades later, in the touch-sensitive switches used on some modern lamps and clock radios. And the article typifies the spirit of free-wheeling creativity that characterized this phase of radio history.

Ten years later, in 1936, Radio Craft published an article describing a more artistic use of a capacitance plate in the floor. The Terpsitone was a modified Theremin electronic instrument, controlled by dance movements rather than by moving one's hands in the air.

Other articles in this issue include:

  • The Broadcasting Situation, by Hugo Gernsback
  • "Wired Radio" and its Applications
  • "Ether Fleas"
  • Assuring Safety in Radio Installation
  • "B" Battery Eliminators
  • A Perfect Static Shield
  • Radio-Freqency Amplification
  • A New Rectifier Tube for "A-B-C" Power Units
  • "Echoing Silence"—Part II (fiction)
  • Latest Products of Radio Ingenuity (pictorial)
  • Radio Overseas (pictorial)
  • Radio in Transatlantic Flight
  • Radio News of the Month Illustrated (pictorial)
  • An Autotransformer Receiver (construction)
  • The Infradyne
  • A New Amplifier and "B" Supply Unit (construction)
  • A "Five-In-Two" Receiver (construction)
  • Types of Audio Amplifiers
  • A Unique Nine-Tube Superheterodyne
  • A Sub-Paneled Four-Tube Receiver
  • Methods of Oscillation Control in Stabilized Receivers

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