Patent GB-890438-A (GB)
Title: An impulse corrector with start-stop synchronisation
Inventor: SUSICKY STANISLAV
IPC: H04L25/24
Filed: 1959-02-13
Abstract: 890,438. Code telegraphy. TESLA, NARODNI PODNIK. Feb. 13, 1959, No. 5069/59. Class 40(3). An impulse corrector or regenerator used with sequences of start-stop signals comprises an input circuit responding to the received telegraph impulses, a correcting output flip-flop circuit responsive to the input pulses in conjunction with control pulses for providing corrected output pulses and a continuously oscillating pulse generator connected to a synchronizing circuit which operates in such manner that the. time sequence of the control pulses derived from the continuously running oscillator is brought into correct position relatively to the incoming telegraphic modulation at the instant which coincides with the beginning of the start impulse. In the diagrammatic arrangement, Fig. 5, the incoming signals are applied to a flip-flop device 1K and also to an outgoing corrector flip-flop 2K conjointly controlled by pulses from a continuously oscillating pulse generator G1. The beginning of the start impulse received as a pulse on input Z triggers circuit 1K to condition "1" to produce a positive pulse trigger the flip-flop 3K to the condition 1 in which it remains for a period of 120 m. secs. so that it is not influenced by any of the start polarity pulse appearing in the five information signal elements. The change of 3K to the condition 1 switches the flip-flop 4K to the condition 1 for a predetermined short period, e.g. half the element duration, altering the phase of the oscillator which resumes normal oscillation at the end of the pulse. The length of the pulse is such that the phase of the oscillator output is changed so that first control pulse is generated at an instant which is half the normal element period later than the change of the flip-flop 4K to condition 1, i.e. normally 10 m. secs. after the beginning of the start element. In the detailed circuit arrangement, Fig. 6, the oscillator controlling the pulse generator comprises a transistor T9 connected in a circuit comprising positive feed-back from the secondary of a transformer Tr1 and negative feed-back from a network formed by resistors R37, R38, R39, R40, R41 and capacitors C5, C7. The output from the oscillator transistor T9 is amplified in transistor T8, squared by flipflop transistors T6 and T7, differentiated by circuit C3 and R27, amplified by transistor T5 and applied via capacitor C2 to the circuit 2K constituted by the transistors T1, T2 responsive to the input at contact a of receiving relay A and passing the corrected or regenerated output via amplifier transistors T3, T4 to one or the other winding of relay B with its contact b connected to the outgoing line. The phase-shift of the oscillator is effected by a transistor T10 operated by a pulse from the flip-flop T11, T12 constituting the circuit 4K of Fig. 5. The circuit T11, T12 is changed over for a predetermined period determined by the circuit C9, R44, R45 by a pulse produced by the changeover of the flip-flop T13, T14, forming the circuit 3K in responseto a positive pulse passed to the base of the transistor T13 and to the collector of the transistor T14 when the contact a of relay A moves to the position Z in response to the start element. The change-over time of the circuit T13, T14 is determined by the values of capacitor C10 and resistor R54, and is normally arranged to be about 120 m. secs. so that the circuit T11, T12 restored to its normal condition after a short period allows the circuit T13, T14 to be unaffected by the code information elements and to change back at about the beginning of the stop element of the start-stop code combination.