Patent GB-524917-A (GB)
Title: Improvements in or relating to telegraph transmitters and receivers
IPC: H04L13/10
Filed: 1939-02-10
Abstract: 524,917. Photo-electric distributers for startstop telegraphy. STANDARD TELEPHONES & CABLES, Ltd. (Hatton, W.). Feb. 10, 1939, No. 30967. Divided out of 4432/39. [Class 40 (iii)] Specification 374,945 has already described photo-electric distributers for telegraph systems but has not mentioned the application to " start-stop " telegraphy. According to the invention, similar photo-electric distributers are used for transmitters and receivers of "start-stop" telegraphy. Transmitter. As shown in Fig. 2, the photoelectric distributer comprises five circuit lamps L1 ... L5 and a stop-lamp SPL in a box TB divided by partitions S1 ... S6 and closed by a lid carrying an additional partition S7 enclosing a " start sector STS without a lamp. A central cylinder CL formed with a slit SL and provided with a mirror MR, Fig. 3, is adapted when rotated to throw the light from the several lamps in succession on to a photo-electric cell PHC connected through an amplifier to a telegraph relay or static modulator. The stop lamp SPL is permanently lighted and the circuit lamps L1 . . . L5 are controlled by keys, switch brushes, or record tapes to determine a code which is sent by one rotation of the cylinder CL. During the time the slot SL traverses the start and stop sectors, there is time for the lamps L1 ... L5 to be changed to the next code. For automatic working, an indication for determining the instant for changing the code is given by a contact controlled by the rotating cylinder or by the use of a brighter lamp for the stop lamp whereby a greater output is produced by the amplifier and operates a marginal relay to advance the device controlling the lamps L1 ... L5. The lid with the partition STS may be rotatably adjusted to vary the duration of the start signal. This enables the transmitter to be used to measure the receiving margins of teleprinters. A pointer PT indicates the setting of the lid. For code sending or margin testing, the rotating cylinder CL may be mounted direct on the shaft of a synchronous motor running at 375 r.p.m. Receiver. As shown in Fig. 6, the photoelectric distributer comprises five photo-electric cells PH1 ... PH5 in sectors in an annular casing RB having two more sectors without cells corresponding to the period of the stop and start signals. A chamber RCL containing a Neon lamp NT rotates within the annular chamber to enable the lamp to flash light through slots in the chamber and casing to the cells PH1 ... PH5 in succession according to the code received by a polarized relay Lr. The rotation of the chamber RCL closes a switch ON in the circuit of the Neon lamp while the chamber is rotating past the cells. At the commencement of reception, the motor (not shown) driving the chamber RCL is energized over terminals 9, 10. The chamber is driven through a clutch controlled by magnet C. Relays Ar, Cr, Dr, Er associated with the polarized relay Lr serve for the various controls. The output of the cells PH1 ... PH5 operate amplifiers A1 ... A5 connected to relays Pr1 ... Pr5 which in turn operate relays Br1 ... Br5 locked and unlocked for each signal code. The Provisional Specification describes a different form of receiver in which photoelectric cells are also provided in the start and stop sectors of the annular casing.