Patent GB-247550-A (GB)
Title: Trunking system of radio distribution
IPC: H04H20/81
Filed: 1926-02-04
Abstract: 247,550. Colladay, E. F., (Assignee of Clement, E. E.). Feb. 14, 1925, [Convention date]. Systems for transmitting music &c.-The out-put currents of a wireless broadcast receiver are repeated to. telephone subscribers desiring such service by individual amplifiers at the exchange. A system is described involving wireless distribution from a studio and relay station to a number of exchanges, with means for testing the broadcasting at all the exchanges from a common point. A subscriber may have the choice of several programs, and may be switched through to the studio station to broadcast his own voice. When subscriber A<1> plugs his loud speaker 64 into jack J<2>, the energization of line relay L<1> lights lamps L<2> and 36 at the telephone and broadcast operators' positions. The subscriber flickers these lamps by the key 63 to indicate that he desires broadcast service, and the broadcast operator inserts a dummy plug 10 in the jack 9 to connect the subscriber's line through battery B, a supervisory relay 42, and transformer 19, 20 to the output side of the subscriber's individual amplifier 37. The input side of the amplifier is connected by the relay 42 to the program bus-bars 27, 28 which receive the low-frequency output from the wireless receiver 29 or 89. The relay 42 also closes the filament circuit and connects battery to wire 3 to energize relay L<3> which cuts off the line relay. Special busy tone 35 is also connected to the wire 3 so that a telephone operator testing the line with a plug P<1> is informed that the subscriber is only busy on broadcast service and may be interrupted. When the jack J<2> is unplugged the relapse of relay 42 lights the lamp 36 steadily, to indicate that the plug 10 should be withdrawn. The studio and relav station with its microphone 40 and modulator 41, is represented in Fig. 3. To permit a subscriber to broadcast, he may be connected to the modulator 41 by an exchange cord P<1>, P, Fig. 1, trunk 101, 102, and plug 48. In the system shown in Fig. 5, the studio and relay station 96 radiates to three exchanges 91, 92, 93, and the 'broadcasting at all the exchanges may be tested from a common point 97 from which an order wire and test trunk extend to each exchange. For example, to test the performance of the amplifier 37, the testing official gives instructions over an order wire 84 for the cords 85, 86 to be plugged as shown, and can then connect his testing apparatus 98, Fig. 4, and listening set 74 to the input and output sides of the amplifier by plugging them into the circuit 78, 79. Testing apparatus is also provided at the studio and relay station, Fig. 3, from which order wires and test circuits extend to the several exchanges. For example, an official at this station may listen to the output of the wireless receiver 29 over a circuit 46, 50, 51, 57, 55, and while this is being done the receiver 29 may be disconnected from the bus-bars 27, 28 and a second receiver 89 connected in its place. The low-frequency output of a wireless receiving station may be connected to the exchanges by wire trunks. On the other hand, the broadcast currents may retain their high-frequency form until they reach the subscribers' stations, in which case these are provided with detectors and the output connections of the amplifiers 37 are suitably modified. The Specification as open to inspection under Sect. 91 (3) (a), describes also the modification shown in Fig. 6 (Cancelled), in which the subscriber by means of his supervisory relay 42 may control a step-by-step switch S to select one of several program circuits, one of which may be an announcer's circuit AS. This subject-matter does not appear in the Specification as accepted.