Telegraph system

Abstract

Abstract 547,593. Type-printing telegraphy. CREED & CO., Ltd., and THOMPSON, A. E. July 1, 1937, No. 19137. [Class 40 (iii)] In a step-by-step field telegraph, impulses are sent to line at an even rate and signalling is effected by repeated reversals of polarity in order that, in the interests of secrecy, the impulses may be prevented from causing clicks in a telephone receiver coupled to the line. A continuously driven shaft a causes a contact r2 to be reciprocated by a cam s so that impulses are sent to the line r at an even rate, the line being disconnected in the intervals between the impulses. The polarity of the impulses is determined by a contact n2 whose position is set by a cam n on an intermittently rotating shaft b which is driven by the shaft a through a clutch c. The clutch is controlled by linkwork, part of which is carried by an arm h rotating above a disc i having letter keys such as k arranged around its periphery. When the transmitter is idle, the arm h is held by the key last operated, and signals of uniform polarity are sent to line ; but when a fresh key is depressed the arm is released and rotates until that key is released. The clutch c, released so long as the arm h is rotating, causes successive impulses to be of opposite polarity during the signalling of the letter. Instead of intermittently disconnecting the line, the contact r2 may intermittently earth it, Fig. 3 (not shown).

Inventors

• 👤 Thompson Alfred Edward

Bibliographic Details