GB436188A - Improvements in or relating to telegraph receivers - Google Patents

Abstract

436,188. Induction relays. SOC.FRANCAISE RADIO-ELECTRIQUE, 79, Boulevard Haussmann, Paris. Feb. 15, 1935, No. 4970. Convention date, Feb. 15, 1934. [Class 38 (v)] [See also Group XL] Telegraph signals, sent by varying the phase of a radio frequency signalling current to distinguish " marks " from " spaces," are received by beating the incoming signal with a local polyphase current of about the same frequency, setting up a rotating field by the polyphase beat current, and utilizing such field to actuate indicating- apparatus. The system does not require exact synchronism between the incoming signal and the local source. In the receiving relay shown, the coils 14a, 14b are located in slots in a rotor mounted on a vertical spindle, the two-phase beat current being led in through slip rings 13. The rotor can turn freely within a stator formed by semicircular magnets 16 with upstanding like poles 17 separated by air gaps. A magnetic needle 18 is freely pivoted at 19 on the rotor spindle and passes through the two gaps. At one end the needle is centralized by light springs 21 and the other end lies between fixed contacts 20. When signal transmission is started, the rotor slowly rotates at the beat frequency (or is stationary if the local oscillator is in strict synchronism) and the needle lies between the contact 29. With a sudden change of phase due to keying, the rotor tends to jerk forward or backward, but is prevented by its inertia. Owing to the change of flux direction in the rotor, however, the light needle 18 will be displaced on to one or other of the contacts 20 which may be connected in the circuit of a recorder or telephone. In a modified construction of relay, Fig. 6 (not shown), the stator is divided in a horizontal plane, the lower sections being permanent magnets, whilst the upper sections with the upstanding arms 17 are of soft iron.