Patent GB-854083-A (GB)
Title: Communication equipment
IPC: H04L17/24
Filed: 1956-11-09
Abstract: 854,083. Telegraphy. SMITH-CORONA MARCHANT Inc. Nov. 9, 1956 [Nov. 16, 1955], No. 34339/56. Class 40(3). The invention relates to a communication system, more particularly for use with aircraft, and like vehicles in which, in conjunction with a radio transmitter and receiver, there are provided a telegraph keyboard transmitter, a telegraph page printer and a storage unit comprising a magnetic tape recorder. The units are interconnected and associated with control means comprising a multi-position switch and relay switching circuits whereby the equipment may be operated to provide the following facilities: (1) transmission of messages from the keyboard with the printer monitoring the transmission, (2) transmission of messages recorded in the storage unit with the printer monitoring the transmission, (3) recording of messages from the keyboard unit in the storage unit with the printer monitoring the signals being recorded and (4) reception and printing of incoming messages. A call system is associated with the receiver whereby the printer may operate to print only messages which are preceded by a predetermined call sign. This system may be operated so that either messages identified by the call sign for a particular vehicle e.g. aircraft, or messages identified by a call sign for a group of aircraft, are printed. General. The system uses the normal five unit mark/space code combination, the stop signal being one and one-half elements and the element duration being 22 milliseconds. Operation proceeds under the control of a counting chain which times the signal elements the chain comprising eight stages which are triggered in sequence at element intervals, the seventh stage however being arranged to operate at half element intervals and serving in conjunction with the eighth stage to time the one and one-half element stop signal. Each keyboard operation sets up the five mark/space code conditions of a combination simultaneously, briefly thereafter closes a universal contact and locks the keyboard against further operation. The code conditions are presented simultaneously to the printer and storage unit and the universal contact initiates a cycle of operation of the counting chain. During transmission from the keyboard, the counting chain reads off and times the code conditions in sequence applies a transfer pulse from the first stage to the printer to cause printing and applies back an unlock pulse to the keyboard from the sixth stage. For recording keyboard messages in the storage unit, the universal contact also triggers the storage unit to make a cycle of operation, the storage unit including a commutator which transfers the code conditions sequentially into a recording head. The unlock pulse for the keyboard is made in this case to depend on the completion of the operating cycle in both the printer and storage unit. Transmission from the storage unit is effected by firstly transferring sequentially derived code elements via the commutator to a register circuit, where they are stored simultaneously, and then reading them out from the register sequentially for transmission under the control of the timing chain. The register conditions are also presented simultaneously to the printer, the timing chain furnishing a transfer pulse from the second stage to effect printing and a release pulse to the register from the seventh stage to clear it for a subsequent code combination. During reception of incoming messages, each start element initiates a cycle of the timing chain and causes the code elements to be read off and stored in magnetic memory cores. The core conditions are read out simultaneously to the register circuit by a pulse from the eighth stage of the counter and from there are presented to the printer. A transfer pulse to effect printing is also applied from the eighth stage via a delay circuit, and a release pulse applied to the register from the seventh stage. Details. The invention is described with reference to a circuit and wiring diagram for the complete system. This does not permit of abridgement as a whole, but the more important features of the invention are detailed in the following paragraphs. Transmitter keyboard circuit. Fig. 3 (not shown). Depression of a key displaces five code bars and causes simultaneous actuation of five contacts in accordance with the mark-space code combination of the signal to be transmitted. The contacts cause corresponding operation of a group of five code relays and the settings of the relays are then read off in sequence under the control of a timing chain (see below) and employed to control a relay which keys the radio transmitter. A universal bar, located at the back of the code bars, is operated each time a key is depressed and closes a contact slightly after the setting of the code bar contacts. The contact operates a relay and causes the application of a potential to a start gate in the counting chain to initiate a cycle of operation. Depression of any key also locks the keyboard against further operation until a release solenoid is energized. When the system is set up to transmit from the keyboard a signal to operate the release solenoid is obtained from the sixth stage of the counting chain. When the system is set up to record keyboard messages in the storage unit, a signal to operate the solenoid comes from the last to operate of a switch in the storage unit which closes when the recording head has completed its cycle of operation and a switch in the telegraph printer which closes when the main drive shaft is restored to its stop position. Provision is made to interrupt the circuit by a contact actuated when the end of the magnetic tape is reached. The keyboard is constructed so that holding a key depressed does not cause repeated transmission. The space bar however is arranged to permit repeated transmission by the provision of a contact actuated by the space bar which bypasses the contact controlled by the universal bar. An indicator lamp is provided on the keyboard which is operated by an end-of-line contact on the printer. A further lamp is provided controlled from a tape position contact in the storage unit to indicate when only five lines of capacity remain available. The keyboard mechanism Figs. 14-19 (not shown), forms the subject of Specification 854,084. Telegraph printer circuit, Fig. 5. The printer is a type-wheel page printing unit in which the typewheel is located behind the recording medium which is in the form of paper bearing a black material which is in turn covered by light material on the operative face. The printing hammer strikes the operative face to force the medium against the type-wheel. The portion of the light material over the raised character is broken exposing the black material to form the recording The periphery of the type-wheel is divided into 32 equal character spaces and the wheel is mounted on a shaft for rotation to effect character selection. The shaft also carries a sixteen toothed stop wheel by which the shaft rotation may be arrested. The stop wheel is associated with two solenoids E801 and E802 which are spaced about the wheel so that one is operative to stop the shaft in 16 positions and the other to stop the shaft in 16 intermediate positions to provide a total of 32 positions. Associated with the shaft there are also two 16-way commutators S801 and S802, the wipers of which rotate with the shaft, and the apparatus functions to cause a potential to appear from one of the commutators at the appropriate instant to energize one of the solenoids to cause the type-wheel to be arrested at the correct character position. Signals to be recorded, whether originating from the transmitter keyboard, storage unit or radio receiver, cause operation of the five code relays (see above). The contacts of the relays cause earth to appear simultaneously on one or the other terminal of five pairs of terminals 1-6, 2-7, - 5-10 in accordance with the, mark-space code combination. Connections extend from the terminals to the segments of the commutators via rectifier networks CR801-CR804. A negative potential is applied to the input of networks CR801 and CR802 from the junction of resistors R805, R806. In accordance with the selective combination of earths applied to the networks from terminals 1-10, the negative potential is allowed to pass through only one of the commutators and at only one of the 16 possible paths through that commutator. By this means, in accordance with the telegraph code combination, an impulse is produced at the correct one of 32 intervals to stop the type wheel and select the corresponding character. The potential from the commutators cuts off either amplifier V801A or V801B and fires an associated thyratron V802 or V804 to energize stop-wheel solenoid E801 or E802. To initiate printer operation a transfer pulse is applied to tube V805 to energize a solenoid E803 which operates a one revolution clutch between the drive motor and a main shaft which drives the type-wheel shaft. The same pulse is applied to tube V803 which is effective to cut off whichever of thyratrons V802 and V804 is conducting to de-energize the stop wheel solenoid and release the type-wheel from its previously set position. Dependent upon the use to which the recorder is put, the pulse is produced under the control of (1) the keyboard universal bar contact, (2) the magnetic recorder or (3) the telegraph receiver. Supervisory lamps 802 and 803 indicate respectively whether the signals controlling the printer originate from the transmitter keyboard or store, or the radio receiver. The printer mechanism, Figs. 20-38 (not shown), forms the subject of Specification 854,085. Storage unit, Figs. 4 and 8 (not shown). The storage unit comprises a magnetic tape recorder and reproducer utilizing a steel tape of a width sufficient to accomodate five code elements. Recording and reproduc