Patent GB-794522-A (GB)
Title: Printing telegraph signal normalizer
IPC: H04L5/24
Filed: 1955-07-19
Abstract: 794,522. Code telegraphy. DINGLEY, E. N. July 19, 1955, No. 20866/55. Class 40 (3). Printing-telegraph apparatus in which signals comprising start and stop elements are passed intermittently by the operation of a start-stop distributer to alternate groups of storage members, and the stored signal elements are repeated by a continuously running distributer to an output circuit and synchronous receiving printing telegraph apparatus, incorporates a differential circuit arrangement provided with a first group of correction circuits for adjusting the rate of the said signal distributer and its synchronously operated printing - telegraph apparatus to equality with the average rate of said first distributer when the intermittent start-stop signals are being normally received and with a second group of correction circuits for changing the effective average rate of said first signal distributer to equality with the rate of the second signal distributer when the intermittent start-stop signals received by the input circuit have been mutilated, for example, by atmospherics or fading. The arrangement is described in connection with a multiplex regenerator link receiving synchronous telegraph signals and providing at its output start-stop signals having a time cycle less than that of the synchronous input signals. At the end of a predetermined number of characters the multiplex channel provides a blank signal so that the intermittently operated distributer is arrested for one revolution in relation to the continuously running second distributer which rotates at a slower speed corresponding to the synchronous telegraph signals. In response to the start impulse from the start-stop regenerator relay 2 releases and relay 6 de-energizes, connecting clutch magnet 9 via contacts 6a, 6b to a terminal T which normally receives voltage over released contacts 60c, 61c off relays 60, 61, Fig. 2. The start-stop distributer D2, which is driven by a clutch 17 from motor M2, applies via sequentially-closed contacts W1 ... W5 and armatures 11a ... 15a the received impulses to sets of relays 21 ... 25 or 81 ... 85. The storage of the pulses on the first or second set of relays depends on the positions of the armatures 11a ... 15a which are controlled by a relay 16 energized and de-energized at terminal P during alternate revolutions of the distributer D2 by a switch F5 operated by a cam 29 driven by 2: 1 reduction gearing 27, 28 from the shaft 19 of the distributer. The relays 21 ... 25 and 81 ... 85 lock up when energized and the combinations set up are passed over armatures 31a ... 35a and contacts Z1 ... Z5 sequentially closed by cams of a distributer D1 to an output relay 90 with contacts 90a, 90b connected in the circuit of synchronously - driven printing - telegraph apparatus. The positioning of the armatures 31a ... 35a to determine the operative set of relays is controlled by a relay 30 which is energized and de-energized at terminal 2 during successive revolutions of the distributer D1 by a switch F6 operated by a cam 38 driven by 2 : 1 reduction gearing 41, 42 from the shaft 37. A source of alternating current having a frequency equal to a multiple of the character rate of the receiving printing-telegraph apparatus is fed from terminals t, t<SP>1</SP> to a relay 50 through rectifiers 54, 55 and a balancing resistor 56. A cam 52 driven from the shaft 58 of a motor M1 which drives the shaft 37 of the distributer D1 through a reduction gear 36 has lands operating a member 51 closing contacts 51b, 51c for intervals arranged in phase quadrature with contacts 50b, 50c closed by relay 50 and operating so that variations in speed between the printing-telegraph receiving apparatus and the distributer D1, driven from the motor M1, vary the period of simultaneous closure of contacts of 50c and 51b and the field current through winding 53 to decrease or increase the speed of the motor M1. The shafts 19, 37 are coupled to a differential gear mechanism DM, the carrier 47 operating 1: 1 gearing 45, 46 so that the cam 43 is rotated through one-half of the rotational phase difference between the shafts 19, 37. With the rotational speed of shaft 19 greater than that of shaft 37, the distributer D2 acquires an increasing lead over the distributer D1 and after a predetermined number of characters, the generation of an all mark signal from the multiplex output to relay 2 arrests the distributer D2 so that at the end of that signal the distributer D1 is slightly in advance. During this process, which continues until the distributers reach phase agreement, the phase displacement between the shafts 19, 27 varies continuously, and the cam 43 oscillates gradually between minimum and maximum positions in the clockwise and anticlockwise directions. The cam 43 carries a projection p which operates switches F1 ... F4 and F7, F8 and is arranged to correct the action of distributer D2 when the allmarking signal at the end of a number of characters is mutilated so that it has a start element and releases distributer D2 and when an effective signal is distorted so that its initial start element is absent. In the first instance, the extra rotation of the cam 43 will cause switch F3 to close and operate relay 61 opening contacts 61c so that clutch magnet 9 does not operate when a character with a normal start element is received. At the end of this signal, due to the retardation of shaft 19 relative to shaft 37, the cam is in the position it would have occupied had the blank character been correctly received. In the latter case, i.e. when a start element is mutilated, it is shown that by the retardation of the cam 43 and the operation of switch F4, the relay 60 is operated and contact 60c opened, so that depending on the position of the cam 43 when the mutilation took place, the distributer D2 is arrested for one or more revolutions with the result that the position attained after a number of signal periods is the same as that which would have been reached if the mutilation had not occurred. Switches F1, F2 which are not operated when the cam 43 makes its normally limited oscillatory motion, are actuated when the speed of the receiving printing telegraph apparatus decreases or increases respectively, relatively to the transmitting rate as translated by the operating speed of the shaft 19 and advances or retards the cam projection p beyond its normal limits. The closure of contacts F 1 is effective to increase the speed of the printing-telegraph apparatus so that via the contacts of relay 50 and contact member 51 operated by cam 52, the motor M1 is speeded up and the speed of the distributer D1 increased. Similarly the closure of contacts F2 operates to decrease the speed of the distributer D1. Specification 670,759 is referred to.