Patent GB-453462-A (GB)
Title: Improvements in or relating to picture transmission systems
IPC: H04N1/327
Filed: 1935-07-06
Abstract: 453,462. Copying telegraphy. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Dowd, A. D. ; 78, Grove Street, Montclair, New Jersey, and Weaver, A.; 24, Hillview Avenue, Port Washington, New York, both in U.S.A.) July 6, 1935, No. 19344. Convention date, July 7, 1934. [Class 40 (iii)] In a picture-transmission system comprising a plurality of stations each equipped with picture transmitting and receiving apparatus and connected with each other by an electrical transmission path, conditioning means are provided at each station under control of an operator at that station for conditioning the system for picture transmission in one direction only between that station and one or more of the other stations. In addition one-way or two-way telephone communication may be provided between the stations. Before a transmission commences, the operator at a station A (Fig. 2) operates switches 51, 52 connecting his telephone equipment to the line and announces that he wishes to transmit a picture to a number of stations including for example, the station K, Fig. 7, and at the same time operates a key 23 which initiates switching operations throughout the transmission path to produce a visible signal at that station. If further telephone communication is to take place, an auxiliary stop key 25, is operated. Subsequently the key 23 is again closed, and an adjustable stop 24, co-operating with a carriage carrying the scanning apparatus for the picture to be transmitted, is set. On operation of the key 23, relay 26 operates, removing at contact 29 a short circuit of the transmitting amplifier 19, locking up over its contact 28 and lighting the sending lamp 36. In addition, ground is connected over line h to a sending relay 64 located at a central office B. At its contact 68, relay 64 transmits an impulse over wire a to a bridging repeater station C where, with the switches 106, 124 operated according to the location of the receiving station, a relay 131 effects the operation of relay 135 to place ground on a terminal of winding of relay 137 which pulls up and illuminates lamp 139 to indicate that station C is set up to transmit pictures to the line j, k. Relays 107 and 116 are also energized over contacts of the switches 106, 124 to connect the lines a, band j, k through the bridging network 109. Relay 137 applies potential to the line j leading to a repeater station E (Fig. 4), operating a relay 209 which through a relay 213 operates a relay 210. The contacts of this relay short circuit the input to the amplifier 206, effect the lighting of a lamp 212 indicating that the circuit is conditioned for transmitting from line j, k to the fourwire circuit n, o, p, q and apply ground and battery to the lines p, q respectively, leading to a relay 316, Fig. 5, controlling relays 317, 319 to open the circuit of a motor 314 associated with an attenuation equalizer arrangement 310 controlling attenuators 304, 308, associated with the transmission of telephone currents. The current through relay 316 also flows through lines tu leading to a further repeater station G, Fig. 6, (not shown, and similar to Fig. 4), where a lamp is lighted to indicate the direction of transmission through the system and the amplifiers for transmission in the opposite direction are short-circuited. Relay 567 at the central office J (Fig. 7) operates and over line h<1> operates relay 531 at the station K, lighting the lamp 532 indicating to the operator there that the system has been conditioned for picture transmission. The operator at this station operates start-key 582 which energizes relays 583, 586 and 588 to condition the receiving apparatus so that it can be set into operation from the transmitting station. The operator at station A actuates a key 37 which operates a clutch magnet 39 for the transmitting apparatus and which also interrupts the carrier current produced by light 12 and light-valve 13 in conjunction with an oscillator 14. The interruption of the carrier current releases relay 586 at the station K closing the circuit of a clutch magnet 591 to start the receiver apparatus into action, as described in Specification 434,336. When the picture has been transmitted, a stop 24 mounted on the transmitting apparatus opens the circuit of relay 26, which initiates switching operations for removing the direct-current control from the system which is restored to its normal condition in which it is available for two-way telephone transmission. An alternative arrangement is described in connection with Figs. 9 to 16 (not shown), in which each station is provided with means to prevent the receiving apparatus at that station from being controlled from a distant station when it is engaged in transmission to a distant station. Each station is provided with a monitoring meter by which the output from test pictures is checked and transmitted to the distant station before the transmission of the picture is commenced.