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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