Patent GB-338970-A (GB)
Title: Improvements in interpolating arrangements for electric telegraphs
Filed: 1929-08-29
Abstract: 338,970. Electrical Research Products, Inc., (Assignees of Knoop, W. A.). Dec. 31, 1928, [Convention date]. Restoring imperfect signals; distributor systems; type-printing telegraphs.- In a synchronous system, impulses of unit length which are so attenuated that they do not operate receiving or retransmitting relays, are interpolated from a local source by polarized relays in which the line and interpolated voltages are superimposed on the same windings. At the sending station, Fig, 1, are nine transmitters A - - I, arranged in groups of three and so connected to live segments A1, B1, C1, - - that the first impulse from transmitter A as a brush passes over the ring set 11. At the receiving station Y, Fig. 2, the segments of the Deceiving ring set are con. nected to three relays 13, 14, 15, of which the armatures are connected to ring sets 16, 17, 18, concentric with the receiving ring set by brushes 20, 21, 22. The live segments which alternate with dead segments of rings sets 16, 17, 18, are connected to slow-acting printer magnets and are spaced so that the segments A<1>1, B<1>1, C<1>1, A<1>2 - - are engaged in sequence. When impulses of unit length are transmitted and no effective impulse is being received, the armatures of the relays 13, 14, 15 engage alternately contacts of opposite polarity, and if an armature is in engagement with its positive contact as a brush passes over the corresponding live segment of a printer ring, the printer magnet operates. Assuming that as the brush 19 passes over segment A no effective signal is being received, and that the armature of relay 13 is in the position shown when the brush 20 passes over segment A<1>1, a circuit extending from the positive pole of battery 26 through the armature of relay 13 to the negative pole of battery 27 is complete and magnet A<1>1 operates. As the brush 19 passes on to segment B1, a circuit is closed from ground at resistance 30, through the brush, winding of relay 14 and the armature of relay 13 to positive pole of battery 26, and the armature 14 is operated to its left hand or negative contact. As the brush 21 passes over segment B<1>1, the circuit extends from the negative pole of battery 26 through the armature of relay 14 to the negative pole of battery 28, and the magnet B1<SP>1> does not operate. When a signal of two or more units' length is transmitted to the line, the line current holds the armature against assuming a position of opposite polarity with respect to the armature of the previous relay, and according as the long impulse is positive or negative, the corresponding printer magnets do, or do not, operate. At the end of a long impulse when the line current has diminished to zero, the biasing current from the interpolating battery 26 operates the succeeding relay to a contact of opposite polarity with respect to the polarity of the preceding long impulse. In alternative arrangements each relay is incorporated in a circuit including one or more thermionic valves. In one arrangement, Fig. 3, associated with the interpolating relays 41, 42, 43 are pairs of valves 50, 53, - - and printer relays 57, 66, 75. If a long signal (two or more units) of positive polarity is being received, a voltage drop occurs across resistance 45 and is applied through condenser 46, ring 47 and the brush to a condenser 49 and grid of the valve 50, which Motives a normal negative bias from a battery 51. As the brush engages segment A, a positive charge is stored on condenser 49 and this charge impresses a positive potential on the grid, thereby increasing the space current in the valve 50 and left-hand winding of relay 41. At the same time, the current flowing, through the resistance 52 makes the grid of the valve 53 more negative so that the current in the right-hand winding of relay 41 is decreased. The armature of relay 41 engages its right-hand contact and current passes, from battery 56 through the winding of relay 57 to bring its armature to the right hand or positive contact. As brush 59 passes over segment A1, the batteries 56 and 61 augment each other and the printer-magnet operates. Current flowing through a resistance 58 applies to the grid of valve 62 a negative potential, and if no signal is received, the armature of relay 42 will be operated to its left-hand or negative, contact. If the signal is assumed to be positive, and two or more units in length, the voltage-drop across resistance 58 is overcome by the signal voltage applied to the grid of the valve 62 and the relays again operate as described for the preceding circuit, so that as a brush 67 passes over segment B<1>1 the magnet operates. If no effective signal had been received, the current in the left hand winding of relay 42 would have been decreased and the armature of relays 42, 66 operated to their left hand or negative contacts, with the result that as brush 67 passed over segment B<1>1 the printer magnet would not have been operated. Alternative arrangements include the use of an even number of pairs of valve-operated relays with an appropriate number of printer ring sets Figs. 4, 5 (not shown). One. of the valves of each pair Fig. 5 (not shown) is not affected by the line or the interpolated voltages and acts to establish a balancing current opposite to that of the first valve. Additional arrangements Figs. 6, 7, 8 (not shown) include the use of relay circuits embodying only one valve, in which the interpolating relay is shunted by a resistance and battery, Fig. 7 (not shown), or is inductively coupled to the plate circuit of the appropriate valve, Fig. 8 (not shown), the change in voltage in the primary winding causing an induced current in the secondary winding to operate the armature of the interpolating relay to its appropriate contact.