Patent GB-108763-A (GB)
Title: Improvements in the Art of Telegraphy.
Inventor: SQUIER GEORGE OWEN
IPC: H04J1/00
Filed: 1916-09-19
Abstract: 108,763. Squier, G. 0., Austin, L. W., and Cohen, L. Sept. 19, 1916. Duplex telegraphs; harmonic and reed telegraphs.-A signalling unbroken alternating current, of a frequency below or within the limits of audition, is superposed upon a duplex system employing an unbroken alternating current as described in Specification 22,265/14. The frequency of the superposed current is greater than that of the duplex systems, and when below the lower limit of audition, a ticker or an audion is used to raise the frequency supplied to the receiver to that of audition as described in Specification 108,230. The superposed current is not large enough to affect the receiver of the duplex system; while the receiver circuit of the superposed signalling current is tuned to a frequency at which the current of the duplex system does not affect it. The transmitter of the superposed current is inductively connected to the line in such a manner that it does not affect the receiver of the duplex system at the same end of the line. Several superposed currents of different frequencies may be superposed on the line; while each end may be provided with a transmitter and a receiver of such current with suitable switching arrangements so that a station may send messages by means of. superposed current for a portion of the day and receive for the remainder of the day. In the arrangement shown in Fig. 1, the stations A and B are each provided with an alternator 1 inductively connected to the line 9 by a transformer 2, 3, and are provided with means 4 for varying the amplitude of the alternations. Each station also is provided with a visual receiving device 7 connected across the balancing condensers 6. The station A also is provided with an alternator 10 inductively connected to the line 9 by a transformer 11, 12. The alternator 10, of higher frequency than the alternator 1, is provided with a device 13 for varying the amplitude of its alternations, and is inductively connected to the circuit of the receiver 7 at the station A by means of a transformer 14, 15 in such a manner that the transformers 11, 12 and 14, 15 balance each other with respect to the receiver 7. A looped circuit 16, 17 tuned to the frequency of the alternator 10 is connected in series with the receiver 7 in order that the current which may exist, due to the lack of balance of the trnsformers 11, 12 and 14, 15, may not pass through the receiver 7. The telephone receiver 21 at the station B is placed in a circuit 19, 20, and 23 tuned to the frequency of the alternator 10 and consequently out of tune with the frequency of the alternator 1 so that current from the alternator 1 has no appreciable efiect upon the receiver 21. In order that the current from the alternator 1 at station B may not affect the receiver 21, transformers 18, 19 and 22, 23 are arranged to oppose each other with respect to the receiver 21. In the modification shown in Fig. 2, the receiver 7 is inductively connected to the line 9 by means of a transformer 24, 25: while the alternator 10 is connected to the line 9 by a transformer 11, 12 and to the circuit of the receiver 7 bv means of transformers 14<a>, 15<a> and 14<b>, 15<b>. In the modification shown in Fig. 3, the superposed current is below the frequency of audition and the line is connected to an oscillatory circuit 19, 20, and 23; while the receiver 21 is shunted bv a ticker 27 or connected to an audion as described in Specification 108,230.