Patent GB-312384-A (GB)
Title: Improvements in controlling means for sound reproducing apparatus
IPC: H04B1/20
Filed: 1928-02-22
Abstract: 312,384. Sayers, W. H., and Electramonic Co., Ltd. Feb. 22, 1928. Receiving-sets combined with phonographs.- Relates to sound-reproducing apparatus comprising a gramophone in which is provided an electric pick-up connected to a valve amplifier for operating a loud-speaker, and in which means may also be provided for switching-over the amplifier from the gramophone pick-up to a wireless receiver when required. According to the invention, starting and stopping means for the gramophone are adapted also directly to operate means for making and breaking one or more of the valve circuits. In the arrangement shown in Fig. 1 a springdriven gramophone is employed, the turntable 1 being stopped or released by a spring- controlled brake arm 3 operated by an eccentric 6 cuts out one or two of the series condensers 3, The disc 7 has a contact arm 9 which, when the brake is operated to release the turntable, bears on a contact stud 10 and completes the circuit of the low-tension battery 14 of the amplifier 11, to the input terminals of which the pick-up 2 is connected. Instead of arranging the contact arm 9 as shown, it may form part of a separate switch, connected to a gramophone brake of the ordinary kind, by lever mechanism or the equivalent. The switch may also control the high-tension current supply for the amplifier. Further, the arm 9 may close a charging circuit for storage batteries, when moved so as to break the connection to the amplifier. If the gramophone is driven by an electromotor instead of by a spring, the switch arm 9 is arranged to control the circuit of the motor simultaneously with control of the circuit of the battery 14. Fig. 2 shows an arrangement wherein an amplifier 11, operating a loud-speaker, may be connected either to a gramophone pick-up 2 or to a wireless receiver 18. The gramophone is in this case driven by an electromotor 25, receiving current from the mains 17, which also supply, through a transformer, a low tension current to the amplifier and the wireless receiver, and, if desired, high tension current also. Two switches, which are to be moved together, are shown, one of them, 19, connected either the receiver 18 or the pickup 2 to the amplifier, and the other, 20, connecting either the gramophone motor 25 or the receiver 18, as required, to the mains. The switch arm 20. when in the neutral position shown, cuts both the motor 25 and the valve sets out of circuit. The amplifier shown in Fig. 2 may be so arranged that when it is connected to the wireless receiver all the valves are brought into use, while fewer valves are used when the amplifier is connected to the gramophone pick-up. Alternatively, two separate amplifiers may be provided. In a further arrangement (Fig. 3, not shown), instead of the separate switches 19, 20 shown in Fig. 2. a single switch combining the functions of these switches' is provided. Another modification consists in arranging a suitable choke between the pick-up and the amplifier, so that disconnection of the pick-up is unnecessary while the wireless receiver is in use.