GB524526A - Improvements relating to blind-landing systems - Google Patents

Abstract

524,526. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd., and ARMSTRONG, L. J. HEATON-. Jan. 31, 1939, No. 3309. [Class 40 (v)] In a monitoring arrangement for an overlapping beam transmitter, the outputs from two similar receivers symmetrically located on each side of the course line are combined, and any deviation from the normal operation of the transmitter is made to operate an alarm. In Fig. 2 the A.F. outputs from the two receivers A and B are opposed across the transformer TR1, and the resultant current is rectified at R to energize the relay winding 1. During normal operation of the transmitter when the resultant current is of a constant normal strength, the relay armature 3 is held midway between the contacts 2, 4 and the voltmeter shows a steady deflection. Alternatively the outputs from the two receivers may be combined in opposition and fed directly to the relay. If the transmission varies from normal so as to affect both of the overlapping characteristics, e.g., failure of the radio or modulation frequency, change in the strength of the beam, broadening or narrowing of the beam, or swinging of the beam from the correct direction, the resultant current will be greater or less than normal, and the aural or visual alarm 5 is continuously operated by the closure of contacts 4 or 2. The voltmeter V indicates the nature of the change in resultant current. If the transmission varies from normal for only a portion of the keying cycle, e.g., by failure of one of the complementary signals, or -by mistiming of the keying relays, the alarm is operated intermittently. In the former case the alarm will operate in the rhythm of the complementary signal that has failed. The alarm may be energized through a delay device so that it is not operated by objects moving temporarily across the beam.