Abstract
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 means of improving reception. In modern times the popularity of this receiver has greatly declined. At first sight it would look as if when listening with both ears to a long distance call or when in a noisy room it would be a great improvement ; but this is rarely the case owing to what is called side-tone, that is, the reproduction by the receiver of room-noise falling on the microphone at the same station. It is far more difficult to sort out the wanted from the unwanted sounds when both are entering both ears, than when one ear alone is used. In the Engineering Supplement to the Siemens Magazine of April a new type of the extra receiver is described. It is pointed out that in certain circumstances it is very useful to have an additional receiver. It enables a third person to listen to the conversation and, if necessary, make notes. As this facility is only required occasionally, and if this receiver were always left in circuit it would permanently 'degrade' the hearing, a switch actuated only when the 'watch' receiver is pressed against the ear is introduced in the circuit. Incidentally, this receiver enables the user to know when he is using sufficient pressure. It is not sufficiently recognized that in everyday use, pressing the telephone too lightly against the ear distorts sounds communicated. In the new table pattern 'neophone' telephone, the extra watch receiver is hung up by a hook. When lifted off and pressed against the user's ear, it is immediately available.
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An Extra Receiver for the Telephone. Nature 140, 230 (1937). https://doi.org/10.1038/140230c0
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DOI: https://doi.org/10.1038/140230c0