Improvements in devices enabling the mechanical vibrations produced by blades, strings, tuning forks, vibrating rods or the like, to be amplified by means of thermionic tubes

摘要

542,121. Musical instruments ; burglar alarms. VASILACH, S., and SOC. DES TELEPHONES PICART LEBAS. Aug. 4, 1939, No. 22657. Convention date, Aug. 10, 1938. [Classes 88 (ii) and 118 (i)] The mechanical vibrations of rods, tubes, or strings in musical instruments, burglar alarms, &c. 'are converted into electrical oscillations by causing the rods, &c. to vibrate in a constant magnetic field, the current induced being fed to an amplifier through a transformer. A rod 1, Fig. 1, is clamped at one end in a block 2 and at its free end 4 is connected by a flexible wire 5 to the primary of a transformer of a valve amplifier. On each side of the rod are arranged the poles of a magnet 3. A number of rods, &c. may be connected in parallel or series or series-parallel and may be struck by key-operated hammers. The same principle may be applied to steel-stringed musical instruments in which case the strings vibrate between the poles of a magnet system, Fig. 5 (not shown).