Receivers for Telephone Handsets

The receivers used for modern handsets are of the capsule type and are made so that they cannot be dismantled in the field. The basic principle of operation is the same as for the receivers considered previously. Methods of construction used and the improvement in frequency response are shown in Figs. 36 and 37.

A modern receiver has a small, yet powerful, permanent magnet which is often made of Alnico. The diaphragm is made of good flux-conducting material. Also, the diaphragm is constructed and acoustically damped so that resonances are minimized.^{34, 35}

The resonant diaphragms of the old receivers produced loud clicks when excited by transients such as those caused by switching. These clicks sometimes caused acoustic shocks that were bothersome and occasionally injurious. Such disturbances are not so pronounced with non-resonant receivers.