AN interesting development in deaf-aids has been recently demonstrated in Wyndham's Theatre, London, and is being installed in a number of cinemas. Hitherto a deaf person in a cinema could frequently be supplied with a listening telephone, operated by an amplifier following a microphone located near the loud speakers behind the screen, or from the actual sound-film amplifying equipment itself, but the user was necessarily tied to his seat by the connecting wire. In the ‘Telesonic system’, made practicable by Messrs. Multitone Electric, an efficient type of deaf-aid is operated by a pick-up coil, in which are induced currents from an energized cable hung round the auditorium or placed under the carpet. In a theatre, a microphone in the footlights operates a specially corrected amplifier of about ten watts capacity, the output of which is fed into the magnetizing cable by a specially designed transformer. On demonstration, the device worked well and adequate audition was obtained, with freedom to move over the whole area of the seats, or even some distance outside this area. The fundamental idea of direct speech or music induction without a radio carrier is not, of course, new, but it is understood that the main feature of the invention is the disposition of magnetizing coils such that cross-talk between adjacent theatres or cinemas using the system is obviated. The normal deaf-aids manufactured by the Multitone Company are now arranged to operate with the ‘Telesonic system’ in theatres.