Improvements in or relating to transducers

851,503. Microphones. STANDARD TELEPHONES & CABLES Ltd. Jan. 9, 1959 [Jan. 16, 1958], No. 1526/58. Class 40 (4). In a microphone in which an enclosed space behind the diaphragm is connected to the outside of the microphone casing by a resonance control tube, the tube also serves as a conduit for the electrical conductors connected to the diaphragm drive unit. As shown in Fig. 3, the drive unit 20 is carried by an apertured frame 21 to the periphery of which front and rear casing portions 10, 11 are sealed. The frame also supports a magnetic diaphragm and slug assembly 22 which may be connected to an outer diaphragm 23 of light alloy or plastic. The resonance tube 19 may be moulded with the rear casing portion 11 in a suitable insulating material such as toughened opaque polystyrene, and is arranged with the electrical conductors 17, 18 leading to the drive unit so that it opens out at an aperture (not shown) at the front of the microphone. More than one resonator tube 19 may be provided, in which case each conductor may pass through a different tube. A receiver of the deaf-aid type is also described, Fig. 7 (not shown), in which the electrical conductors pass through an anti-resonant aperture in the rear of the casing.