Patent GB-676588-A (GB)
Title: Improvements in and relating to printing telegraph receivers
Inventor: RIDLER DESMOND SYDNEY
IPC: H04L17/30
Filed: 1950-08-21
Abstract: 676,588. Type-printing telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Aug. 21, 1950, No. 20649/50. Class 40 (iii). A printing telegraph receiver comprises means for registering a received code combination, means for setting a type-wheel into rotation from a given angular position, means for counting the number of character positions through which the type-wheel is rotated and means for stopping the type-wheel in a position determined by comparison between the number of character positions so counted and a number represented by the received code combination. In the stop position of the system the tube TP1 is in the fired condition and the valve V2 of a multivibrator PG1 is non-conducting, the associated valve VI being conducting. When the start impulse, i.e. a space, is received, a contact ral of the receiving relay RA renders the tube TP1 non-conducting and the lowering of the potential of the cathode of the valve V2 makes this valve conducting and cuts off the valve V1. The multivibrator produces a set of timing pulses at 20 millisecond intervals and at the output of the valve V2 produces " scanning " pulses at approximately 10 milliseconds later than the timing impulses which are applied over resistance R2 to seven cold cathode tubes TD1 ... TD7. In the normal or stop condition the tube TD7 is in the " fired " condition so that TD1 is primed and is in condition to be fired by the first timing pulse. The firing of TD primes the tube TD2 to be fired by the next timing pulse and extinguishes the tube TD7. The pulses produced by the firing of the tubes TD2 ... TD6 are passed to terminals T9 ... T13 leading to the odd-numbered or spacing tubes TC1, TC3 ... TC9 coupled to the even-numbered or marking tubes TC2 ... TC10 of a binary counting arrangement. In the stop condition the marking tubes TC2 ... TC10 are all fired and the tubes TC1 ... TC9 are primed in succession at about the middle of the signal elements. If the received code signal element is a space an impulse is passed via contact ra2 and connection T16 and is effective to fire the tube which is primed by the appropriate timing impulse generated by the tubes TD2, TD6. The positive potential developed across cathode load resistor of the tube TD7 is also applied via the connection T15 to prime the tubes TP1, TR1, respectively, and both these tubes are fired by the seventh scanning pulse applied from the valve V2 over the connection R2, C2, Fig. 5. The firing of the tube TP1 applies a positive bias to the cathode of the valve V2 to disable the multivibrator and the firing of the tube TR1 operates a relay RC. At contact vc1 a driving circuit is completed for the motor 1 which drives the type-wheel 5 through gearing 3, 4 and the gear-wheel 3 operates a cam member 6 closing contacts 7 for each rotatiion of the type-wheel 5 corresponding to the distance between letters. Each closure of contacts 7 applies through connection T6 and condenser C3, having its plates X, Y normally connected to batteries B3, B2, a potential B2+B3 to connection T8 leading to the first pair of tubes TC1, TC2 of the binary counting chain. The successive impulses generated by the rotation of the type-wheel control the firing of the tubes TC1 ... TC10 and the rotation of the type-wheel to bring the appropriate character to the printing position is determined by the number of impulses to be fed into the binary counter-with one or more spacing tubes TC1, TC3 ... TC9 fired in accordance with the received signal-in order that all the marking tubes TC2 ... TC10 are brought to the marking condition. The counter operates on the general principle that each pulse changes over the condition of tubes TC1, TC2, whilst every second, four, eight pulses reverse the condition of the tubes TC3 and TC4, TC5 and TC6, and so on. In the latter condition the change-over from TC9 to TC10 causes a neon tube N5 to pass an impulse to the connection T17 which fires a cold-cathode tube TR2 energizing a relay RD which at contact rdl opens the motor circuit. Grounded battery applied over contact rb3 (unoperated) and rd2 (operated) to connection T7 energizes solenoids 9, 10, 11 in parallel. The solenoid 9 operates a positioning member 12 engaging between teeth of a wheel 13 on the type-wheel shaft, the solenoid 10 actuates a printing hammer 14 to press the tape 8 against the type-wheel 5 and the solenoid 11 moves a pawl 15 over a tooth on a wheel 16 so that release of the member 11 feeds the printing tape 8. Operated contacts rd3 close a circuit for a slow-operating relay RB which on operation locks up over contacts rb1 and connection T1 leading to contacts 17 which are closed when the type-wheel has moved from its normal position. Contacts rb3 open the circuit of the solenoids 9, 10, 11 and apply a ground to connection T2 leading via contacts 22, operated similarly to contacts 17, to close a circuit to the motor 1. The opening of contacts rb2 extinguishes tubes TR1, TR2 so that relays RC, RD release. The opening of contacts rb4 prevents further impulses from passing to the binary counting circuit TC1 ... TC10 during the rotation of the type-wheel to its normal position in which the opening of contacts 17, 22 releases relay RB and opens the circuit of the motor 1. A modification incorporating Figs. 8-11 (not shown), permits the storing of a code combination of impulses on a set of five cold-cathode tubes, whilst the previous combination is being printed. The seventh scanning impulse fires a tube having in its circuit a relay which effects firing of the appropriate tubes in the register counting chain. A slow-operating relay restores the storage tubes to the extinguished condition and operates a relay which has a contact in the circuit which connects the motor to move the type-wheel to its character-selecting position, the circuit of this relay being broken by the relay (RD) operated when the impulses fed to the binary counter are such as to bring it to the final condition with the marking tubes all fired. Specification 636,668 is referred to in connection with the multivibrator PG1.