Patent GB-288142-A (GB)
Title: Method and apparatus for switching reproducers from one device to another
IPC: H04N3/36
Filed: 1928-03-22
Abstract: 288,142. Electrical Research Products, Inc., (Assignees of Reynolds, J. L.). April 1, 1927, [Convention date]. Artificial lines.-In a system for associating a reproducer with a number of transmitters so that separate or collective reproduction can be effected, provision is made for fading out the effect of one transmitter and increasing the effect of another to attain continuity of reproduction. The transmitters are connected through an artificial line or a potentiometer and selective switch mechanism with a reproducer. In Fig. 1 two gramophone turntables 2, 3, working in synchronism with separate picture projectors P. P<1> have their pick-ups 12, 13 connected to opposite end of an artificial line AL arranged in sections connected to contacts 47, 48 arranged around segments 39, 40 below a rotary switch S carrying insulated blocks 37, 38 which bridge adjacent contacts and connect any one with the segment to complete a circuit. to a transformer T<1> conrected through an amplifier 42 to a loud speaker 60. The switch S may be adjusted from various convenient positions by gearing 43, 44, a rack 91 and hand wheels 40, 92, 93 and in its various positions introduces various amounts of attenuation due to the line AL into the circuits of the two transmitters, the effect on one being increased as the other is decreased. A switch 49 may be provided, the closure of which will shunt one or other of the transmitters except when the switch S is on the central contacts 47, 48, and in this position the design of the line AL may, if desired, be such that insufficient energy is transmitted to operate the reproducer. When the line design makes the energy transmitted for this position of the switch zero, switch-controlled by-paths containing sections similar to the line sections may be arranged between the ends of the line and the output circuit. The impedance of the end sections S1, S2 of the line should preferably match the impedances of the pick-up circuits connected therewith. In a modification, the artificial line is constituted by two potentiometer wires with spaced bridges and the switch S is replaced by a slider, the ends of the wires leading to plugs for connection with the output of any two of a series of pick-ups co-operating with records. A section of the artificial line may in this case be inserted at each end of the wires and in the output circuit to the amplifier to keep the relative impedances of the parts of the circuit substantially constant. Fig. 4 shows an arrangement whereby the artificial line may be reduced to one half. Both pick-ups or transmitters T5, T6, are connected to the same end of the line AL, the sections of which are connected to two sets of contacts 108, 109 and 87, 88 arranged parallel to a continuous segment 104 and a divided segment 101, and over which insulated brushes 105, 106 and 107 on a switch arm can be moved. As shown, only one section of the line is connected in the circuit of the transmitter T5 to the loud speaker 60, and further sections can be introduced by moving the brushes. When, however, these are moved sufficiently to contact the segment 101, the transmitter T6 is connected in the circuit and transmitter T5 cut out. As before the line may be designed to reduce the current transmitted, when all the sections are in. to any desired minimum energy, and a by-path 99 may be provided to modify the minimum.