GB521139A - Improvements in or relating to electric signalling systems - Google Patents

Abstract

521,139. Two - way repeating systems. STANDARD TELEPHONES & CABLES, Ltd. (Deloraine, E. M., and Reeves, A. H.). Nov. 1, 1938, No. 20209/39. Divided out of 509,820. Drawings to Specification. [Class 40 (iv)] In a signal transmission system of the double pulse modulation type, that is one in which the momentary amplitude of the original signal is represented in the line by the position of a short signal impulse (which may be a direct current impulse or a burst of high frequency alternating current) in a time period the end of which is fixed by one of a stream of regularly recurring impulses of a similar kind which may or may not be transmitted, the same repeaters are used 'for both directions and are automatically brought into condition for repeating in the appropriate direction by the signals themselves. The repeaters are identical with some of those described in Specification 509,820 and are of the kind in which a multivibrator circuit normally sends direct current impulses to line or in which a high frequency oscillator coupled to the line is periodically quenched and the effect of received impulses is to alter the starting point of the multi-vibrator or quenching cycle. It is shown, since signals arriving in appropriate phase with respect to the impulses generated by a repeater drag the repeater into step with them, that if such repeaters are suitably spaced and if speech at the terminal station always causes an advance of the phase of impulses generated there, the whole system is brought automatically into condition for relaying in the direction of the speech and remains in that condition until speech is originated at the other end whereupon the direc- 'tion of relaying is reversed.