BEFORE the introduction of the modern form of hand micro-telephone instrument and before thermionic amplifiers were introduced on trunk telephone lines, the extra receiver was considered a useful ...

WHEN the radio telephone was first applied to ships at sea about 1929, the ship receivers, connected either to a loud speaker or an operator's headset, were always con the air’ and thus heard all ...

As I noted last week, the term “wireless telephone” in the early 1920s didn’t necessarily mean a device that could both transmit and receive messages. In fact, most radio devices during this time were ...

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