GB142375A - Improvements in telegraph systems - Google Patents

Abstract

142,375. Western Electric Co., (Western Electric Co.). Aug. 11, 1919. Duplex telegraphs; transmitting systems and apparatus; type-printing telegraphs.-In a telegraph system employing currents of opposite polarities, a wandering zero is prevented by grounding the line between successive impulses of opposite polarity and by supplying a positive current to the line between successive negative impulses and vice versa. A rotary distributor is employed provided with a resistance placed between the earthing segments and earth to prevent sparking and to maintain the balance in a duplex system. Construction. The movable contacts 1 - - 5 of a tape transmitter A are connected to the contact-segments 11 - - 15 of a rotary distributor D and to the operating coils of polarized relays 21 - - 25 by leads 6 - - 10 respectively. The circuits of the relays 21 - - 25 contain one winding of relays 26 - - 30. The relays 26 - - 30 are each provided with a second winding connected to the succeeding contact of the transmitter A. The armatures of the relays 26 - - 30 normally connect the contactsegments 36 - - 40 to earth through a lead 20 and resistance 31. The distributor D comprises a ring 17, connected to line 18, and a brush 16. Operation. If for a particular position of the tape the contacts 1 and 2 of the transmitter A be not operated, the relays 21 and 22 and the left-hand windings of the relays 26 and 27 are energized with negative current and the righthand winding of the relay 26 is energized with negative current thereby causing its armature to engage its front contact. The energization of the relay 21 by negative current causes this relay to connect the front contact of the relay 26 to a source of positive current which is connected to the contact-segment 36 by the operation of the relay 26, thereby sending a positive impulse c, Fig. 2, to line 18 between the two negative impulses a and b. If the contact 2 of the transmitter A be operated to connect the segment 12 to a source of positive current, the right-hand winding of the relay 26 is energized by positive current and its left-hand winding the negative current. Under these conditions, the armature of the relay 26 is not operated and the line 18 is earthed through the contact-segment 36 between the negative impulse d, Fig. 2, and the succeeding positive impulse e. If the brush 16 is wide enough to bridge the contact segments 11 - - 15 and the earthed segments 36 - - 40 the resistance 31 prevents sparking at the brush 16.