GB613812A - Improvements in or relating to electrical musical instruments - Google Patents

Abstract

613,812. Electrical musical instruments. COMPTON ORGAN CO., Ltd., J., and BOURN, L. E. A. March 7, 1945, No. 5676. [Class 88 (ii)] In an electrical musical instrument in which the outputs of the generators are controlled by D.C. potentials applied by stops and keys, the potential applied by either alone is insufficient to produce an output, but when both are operative an output is obtained. As applied to an instrument in which the output from a generator, fed over a lead to point f, Fig. 1, is controlled by a thermionic valve 1, the battery 6 provides a negative potential just sufficient to bias the valve to cut-off, but when the stop contact 3 is in its lower undrawn position on contact 4, a further negative potential 7 is applied in series with this. When the stop alone is drawn, contact 3 engages contact 5 and the valve is still cut off by battery 6, but, if the key contact 2 is now closed, the potential applied to the grid is made sufficiently positive by the battery 10 for the valve to conduct. If, however, the key is depressed without the stop being drawn, batteries 7, 10 oppose each other and the valve remains cut off by battery 6. The resistances 8, 11 may be replaced by a variable potentiometer to obtain any desired loudness of tone from the stop. An extension of the circuit in which one generator is made to serve in response to depression of a plurality of keys and stops is described with reference to Fig. 2 (not shown). Specification 613,414 is referred to in the Provisional Specification.