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    • 4. 发明专利
    • Improvements in or relating to telephone systems
    • GB936009A
    • 1963-09-04
    • GB1726960
    • 1960-05-16
    • GEN ELECTRIC CO LTDDEREK PHILLIP ALEXANDER
    • H04M9/00
    • 936,009. Direct-call systems. GENERAL ELECTRIC CO. Ltd., and D. P. ALEXANDER. May 15, 1961 [May 16, 1960], No. 17269/60. Class 40 (4). Connections for effecting two-way conversation may be set up between a first station and any one of a plurality of second stations by manually-operable means at those stations, the connections so set up being, as selected by a caller at any one of the stations, either ones that result from operation of manually-operable means at only the calling station or ones that result from operation of manually-operable means at the called station in response to an indication that the station is being called, which indication results from the operation of manually-operable means at the calling station. As shown, a master station, Fig. 1, is connected to each of a plurality of substations by a separate four-wire line, the equipment shown within the dotted line 1 being duplicated for each substation and the terminals 8, 9, 10 and 11 being connected to terminals 12, 13, 14 and 15 respectively at the corresponding substation, Fig. 2. References containing the letter " O " relate to equipment at the substation. To make a normal call to a substation, the operator at the master station presses a button S2, bringing up a relay A. This starts a multivibrator 22, causing relay F to flash a lamp PA, and operates relay OB (via terminals 10, 14, 15-and 11) which switches on a transistor amplifier 24 and a generator 25 which produces two bursts per second of audio-frequency current. These flash a lamp PO and are heard in receiver 17 as a calling signal. The operator at the called substation answers by pressing button SO1 to bring up relays OD and D, switching off multivibrator 22 and generator 25, producing continuous iliumination of lamps PA and PO, and completing a two-way speech circuit between the substation and channel A at the master station. If button S2 is again pressed, relay E operates to switch the connection from channel A to channel B. Relay X operates on release of button S2, so that subsequent operation of S2 short-circuits relay E and returns the connection to channel A. Lamps PA, PB indicate which channel is in use. Similarly, a substation may call the master-station by use of button SO2, the master-station answering by means of button S1. To cancel a call, button S3 or SO3 is pressed, breaking the holding circuit of relays A and OB (or OA and B). To make a direct call, button S1 or SO1 is pressed, bringing up relays A, OB (or OA, B), D and OD to establish the connection without any action by the called party. The master station may make a group call to all the substations by using buttons GS1, GS2 and GS3 instead of S1, S2 and S3. Specification 936,010 is referred to.