GB721838A - Improvements in or relating to telegraph repeaters - Google Patents

Abstract

721,838. Type-printing telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Jan. 23, 1953 [Feb. 8, 1952], No. 3381/52. Drawings to Specification. Class 40 (3). In a regenerative repeater for start-stop printing telegraph signal combinations transmitted regularly under the control of, say, a perforated tape machine in which a timing circuit is started into operation on receipt of each successive start element, means are provided for adjusting the duration of the time base for each code combination so as to compensate for any time displacement resulting from the receipt of a mis-timed start element. The invention is described as applied to a cold-cathode tube regeneration repeater of the type disclosed in Specification 692,411 in which the timing is controlled by a 5 kc. pulse source triggering a counting chain formed of three multi-gap tubes counting respectively every one, every tenth and every hundredth pulse. A count is initiated on receipt of a start element, and connections are taken from appropriate combinations of gaps in the tubes to open gates examining the received signal to set an output device correspondingly at times corresponding to mid-point of the signal elements. In contrast with the arrangement disclosed in the above Specification, the counting circuit is not brought to rest automatically after a predetermined interval (i.e. 132 ms.), but continues in operation and is placed under the control of the incoming signal so as to be stopped, reset and immediately restarted by the next following start element. This operation is effected under the control of a gate circuit examining the incoming signal during a period extending, in the example given, from 9.2 ms. before, until 9.8 ms. after the correct time of arrival of the start element. The compensation brought about in this way is stated to be effective for variations in the timing of start elements produced by machine variations. In accordance with a further feature of the invention, the counting chain is initially normally set not at the zero position as in Specification 692,411, but at the 10 ms. position, and means are provided for resetting it to the zero and 20 ms. positions to allow respectively for the receipt of a start element over 9.2 ms. early and the complete failure of the start element. This feature is concerned with conditions which may arise due to interference or fading of the signal. A gate is conditioned to examine the incoming signal during the interval 9.2-9.8 ms. before the correct time of arrival of a start element and if a start element is detected the counting is restarted but from the zero position. Thus the premature arrival of the start element is compensated by the added 10 ms., and the timing of the examining periods relative to the true time of arrival of the signal elements is substantially the same as for a correctly timed start element. If the start element does not persist so that it is regenerated when examined in the normal way, a start signal is automatically inserted by forcibly setting the output device. In a similar manner a stop signal is inserted whether or not a mark signal is received during the stop interval. If the start element fails to arrive by 9.8 ms. after the correct time of arrival, the counting circuit is automatically restarted from the 20 ms. position so that the induction of 10 ms. in the count again restarts the correct timing of the examing periods. If the start signal fails entirely it is automatically inserted by forcibly setting the output device. Since the regenerator is here assuming a start element when in fact none has been received, a counting means is provided to stop the regenerator if a number of start elements fail in succession. Provision is made for passing a long space Specifications 636,700, [Group XL (c)], 710,258 and 713,902, [Group XL (c)], also are referred to.