Portable Army Radio Tested (Nov, 1937)

It looks like you should be able to wind up that key in his back and make him march.

Portable Army Radio Tested
A PORTABLE field radio transmitting and receiving set that operates while strapped to a soldier’s back was satisfactorily tested by the Royal Corps of Signals at Alder-shot, England. The device features a special loop-type antenna, standard earphones and a hand microphone. The power supply unit is self-contained.

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2. “Tiny” Walking Radio (Feb, 1937)
3. AUTO RADIO “DE LUXE” (Jan, 1938)
4. Hotel Guests DIAL for Radio Programs (Aug, 1935)
5. Radio Listens In On Phone Calls (Jul, 1936)