Patent GB-786722-A (GB)
Title: Improvements in or relating to apparatus for generating timed pulse trains
Inventor: WRIGHT ESMOND PHILIP GOODWIN
IPC: H04L12/54
Filed: 1953-07-07
Abstract: 786,722. Type-printing telegraphy. STANDARD TELEPHONES & CABLES, Ltd. July 2, 1954 [July 7, 1953], No. 18843/53. Class 40 (3). Apparatus for generating a timed pulse train, which may be employed in the transmission or reception of the elements of equi-unit telegraph signals, comprises a magnetic recording track moved at uniform speed past recording and reading heads in which a recorded mark is read after a predetermined constant time and results in a pulse transmission to an output circuit and also in a pulse applied through a feedback circuit to the recording head which records a mark and this again effects the feedback and transmission operations, the process being repeated until a counting circuit operated by a predetermined number of the feedback pulses suppresses the feedback of the marking pulses to the recording head. Initially a reset signal is applied to gates 1G, 2G, 3G so that 1F3, 2F2 and 3F3 are energized. The output 2F2 causes record head A to record " 0 " in all element positions, and with 3F3 energized, 3F3 will be zero, closing gate 4G so that the second head B will be cut off. When a start signal is received on line 1 the positive part of wave TSW, Fig. 1, opens gate 8G and energizes 1F1 so that the t1 pulse occurring during P1 opens gate 11G and position 1 of 2F is energized and records an impulse in the ST element of one of the recording sections of line 1. At time t2 during the P1 pulse which causes " 1 " to be recorded, gate 12G opens and position 2 of IF is energized so that no further " 1 " can be recorded in any other ST element associated with the line 1. About 30ms from the time the element ST is made " 1," this element reaches the read head where it is detected and passed via amplifier 1A to gate 6G and position 5 of register 1R. This pulse also passes to gate 7G at the time of the pulse P11 and provides an examination pulse for the first permutable element. The remaining elements of the recording section on the drum will be "0." A pulse p3 will have stepped the register 1R so that position 4 is energized and position 5 not energized. The pulses t3 will step the pattern one position as each element passes the read head so that at the end of the fourth element the position 1 of 1R will be energized and positions 2, 3, 4 non-energized. For the PS pulse coinciding with P12, gate 14G will open and at time t1, 15G will open and provide any output on AS, which brings 3F to position 1, and with a positive potential at 3F3.0 and with 4F1 energized, the record head B will record a " 1 " in the ST element of a section allocated to line 1. The t3 pulse for the PS pulse at which ST is recorded as " 1 " steps the pattern on register 1R so that element 1 is now in the position 1 of 1R and since it is "0," 1r1.0 will be positive, and for the following t1 pulse 17G and 18G will be open so that 19G and 16G open causing 4F1 to remain energized and a " 1 " will be recorded. The next t2 pulse will open 20G and position 2 of 3F will be energized, 3F3.0 remaining positive. Again t3 steps the pattern so that the element 2 will be in position 1 of 1R and since it is "0," 1r1.0 will again be positive. For the next t1 pulse 21G, 22G are open so that 23G is open and with 4F2 energized a " 0" will be recorded for this element. Similarly, the same combination will cause a " 0 " to be recorded for element 4 and the recording for this section will be 1100. About 20ms after the first recording passes the read head it arrives at record head A and 2F2 will be energized to erase the original recording. At the same time the recording made by record head B arrives at the read head. As the ST element is " 1," gate 6G provides an output to open 7G with a pulse P11 providing an examination pulse 50ms from the beginning of the start element. The information passes to 1R in which positions 1, 2 will be energized and positions 3, 4 non-energized. The PS pulse coinciding with P12 will open 15G at time t1, as 14G is open by 1r4.0. The output AS from 15G will energize 3F1 and open gate 16G to energize 4F1. As a result 4G opens and a " 1 " is recorded in the ST element for the line 1. The t3 pulse steps the pattern along register 1R so that position 1 will contain element 1 and be energized. Consequently, the next t1 pulse will open 23G since 24G and 22G will both be open, and 4F2 will be energized to cause a " 0 " to be recorded. In the next cycle, t2 cannot open 20G to cause position 2 of 3F to be energized, but the next t3 pulse steps element 2 into position 1 of 1R, and since this element is "0," 1r1.0 will be positive and the next t1 pulse will cause 19G and 16G to open since 17G and 18G will be open. 4F1 will be energized and a " 1 " will be recorded in element 2 of the section allocated to line 1. This time the t2 pulse opens gate 20G, and 3F2 is energized so that the element 4 of the section will be recorded as " 0 " by 21G, 22G and 23G energizing 4F2. During the next three circulation cycles the readings received at the read head provide examination pulses at 70, 90 and 110ms, and produce the modifications of the information stored in the recording section in respect of the number of examining pulses generated. The final recording made by the head B will arrive at the read head after 130ms, and when the t3 pulse occurs for element 4 the recording will be set up on positions 1 to 4 of 1R and positive potential will appear on 1r1.1, 1r2.1, 1r3.0 and 1r4.1. Gate 14G cannot open and the output AS remains at zero potential. Gate 26G is opened by PS at time t1 and provides at ES a positive potential which opens gate 3G to energize 3F3 so that 3F3.0 is at zero potential, thereby closing 4G so that the record head B will be unable to record. 3F will remain in this position for the remainder of the recording section so that the head B cannot record and the head performs a wipe-out action with the result that the recording will be all " 0." The potential at ES is also applied to 27G so that this gate opens and energizes position 3 of IF. For the stop condition of the line, the gate 8G cannot open and the circuit remains in this state until the start element of the next character is received. The pulses PS are provided from a track on the drum having every fourth element as a " 1 " and the pulses TSW, P1 . . . P20 are derived from the series PS. The pulse train t3 is derived from a separate track in which all element positions are " 1 " and the pulses t1, t2 are obtained from the pulses t3 by suitable delay devices. Specification 786,721, [Group XIX], is referred to.