Patent GB-844308-A (GB)
Title: Data transfer apparatus
IPC: G06K13/18
Filed: 1957-04-02
Abstract: 844,308. Statistical apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 2, 1957 [April 2, 1956], No. 10732/57. Class 106 (1). In a machine for transferring characters one at a time from a punched tape to a magnetic tape, there is provided means for checking for and indicating the presence of an error in the transfer of each character and further means controlled by the checking means for blocking the transfer of the erroneous character and for substituting an error signal in its place. The punched tape may be punched on an eightchannel code or on the telegraphic five-channel code. In the former case nine photo-cells 125, Fig. 8A, which sense the eight channels and the sprocket holes, are connected via leads a to h and SP to sockets 126. The eight channel sockets are plug connected to cable 130 from which leads are connected to a translating circuit in which the data in the code used in the punched tape is converted to the code to be used in the magnetic tape. Leads a, b, c, d from cable 130 pass to a Decoder Inverter 132 the outputs of which represent the incoming signals a, b, c, d and also their inverse designated #a, #b, #c and #d, i.e. not a, not b, &c. All these outputs pass to Decoder circuits 134 in which the two groups of four signals are combined to give 16 combinations as indicated on the output leads. These leads are connected to horizontal rows of sockets in the plug board 136. In the same way the lines e, f, g and h from cable 130 pass through inverters 138 to give eight signals which are combined in Decoder circuits 140 and applied to the vertical columns of sockets on board 136. 64 double sockets on this board are connected to 64 leads 0-63 on which Write Entries appear for transfer to the coder 142. The Write Entries are combinations of the six bit code used on the magnetic tape and emerge from the coder as signals on the separate bit lines, designated 1, 2, 4, 8, A and B. These lines enter a cable 144, Fig. 8B, to transfer the signals to a " parity " or " C " bit generator (described below) and check circuits. Any punched tape code can be translated to the magnetic tape code by making appropriate plug connections between the Row and Column Sockets and the 64 Write Entry sockets. The circuits indicated by the blocks 132,. 138, 134, 140, 136 and 142 are repeated in Fig. 8C so as to provide output signals on six lines in the magnetic tape code. These lines represent not 1, not 2, not 4, &c., i.e. #1, #2, #4, #8, #A, #B. Timing pulses.-These are produced in generator 160, Fig. 8A, from signals derived from sensing the sprocket holes of the punched tape by a photo diode. The clock pulses appear on lines 162, 164 and 166, the pulse trains being designated " CP2," " CP ungated " and " CP1 " respectively. These pulses occur simultaneously with the sensing of a character on the punched tape. The ungated CP pulses last for about 500 micro-seconds and occur at the same time as the CP1 pulses which are gated with TM and clock gate signals (leads 168, 170), CP2 pulses are delayed by about 180 micro-seconds and last 100 micro-seconds. CP1 pulses are applied to the decoder circuits in block 134 and the corresponding block in the check comparison circuits. " 0 " bit generator, block 172, Fig. 8B.- The leads in cable 144 representing B, A, 8, 4, 2 and 1 pass to the block 172 in which the " C " bit generator makes the total bits even by adding.a " C " bit if the total number of bits is odd. The " C " bit is recorded in a seventh or " C " channel of the magnetic tape. If a " C " bit is produced it appears on line 174, the " C write bus ". If no " C " bit is necessary, a signal appears on line 176 on which it passes to the " Write Check " circuits in block 276, Fig. 8D. The leads B, A, 8, 4, 2, 1 in cable 144 are connected to Write Circuits in blocks 186 to 191, Fig. 8E. Each circuit has three inputs: a Write Bus, a Write Status and a Write Sample and three outputs: two Bit Write leads and a Write Echo bit lead. The Bit Write leads connect to the Write heads 65 in the magnetic tape writer 109. The tape is erased just in advance of the recording position by an erase coil 66 energized by erase circuits 214 connected to the " Write Status " lead 100. This lead, which is positive when the machine is started causes the writing heads to record on the tape when the write sample lead goes from negative to positive. This happens only after the sensing of the initial code characters which are meaningless characters marking the beginning of the message. They are not transferred to the magnetic tape. A " First Character " circuit in block 218, Fig. 8B, is connected by plug wiring to the decoder panel board to inhibit writing when an initial code character is sensed. When the first meaningful character is sensed a " Write Gate " lead 226 and a First Character lead 228 go positive. Lead 226 passes to a " Write Sample " circuit, block 230, Fig. 8D, in which the write gate signal is gated with a CP2 signal on lead 162 to produce the Write Sample pulse for application to the write circuits as described above. End of record.-A special character " EOR " on the punched tape indicates the end of the record. When this is detected the output lead 240, Fig. 8B of block 282, goes positive during CP1 time. This signal passes to block 242 in which a circuit produces, when an error has been detected, a signal on line 244, termed an Error End of Record Character (E-EOR) and when there is no error a signal on line 246 signal termed a Normal End of Record Character (N-EOR). One or the other of these characters is written on the magnetic tape as is appropriate. The EOR signal on lead 240 also passes to block 250, Fig. 8D, called the EOR Gap and LRC block. The LRC delay lead 252 passes to the First Character block 218 which sends a signal on lead 228 to the PTGO block 122 which stops the paper tape. Following the N-EOR or E-EOR character, a checking character LRC is written which adds a bit to each channel where necessary to make the total bits in each channel even. If there is another record on the punched tape, it is started again and, after a gap, recording on the magnetic tape begins again. Check circuits.-There are four different checking circuits in the machine: a Read Parity check, a Validity check, a comparison check between the outputs of the two coders 142, 156 and another comparison check between what has actually been written on the tape (Write Echo) and the output of the Compare Coder 156, Fig. 8C. Read parity check.-This is used only where the Punched Tape Code contains a parity bit. The block 261, Fig. 8C, is connected to all the output leads of the Compare Decoder Inverter blocks 146, 148. The block 261 has two outputs 263, 269 one for an error signal if there should be an even number of bits and the other for an error signal if there should be an odd number of bits. The appropriate socket is plug connected to the socket 264 of the special character block 267, Fig. 8B. Validity check.-If a character is sensed for which there is no counterpart in the plug connections of board 136 a circuit in block 270, Fig. 8B, provides an error signal. Inputs to the block 270 are b, a, 8, 4, 2, 1 and leads from the Row 0 Column 0 terminals of the Decoder Circuits 134, 140. The error signal on line 273 passes to the Special Character block 267. Coder comparison check.-The outputs of coder 142, Fig. 8A, and coder 156, Fig. 8C, pass to the compare check circuits in block 274, Fig. 8D. The signals on the leads B, A, 8, 4, 2, 1 should always be opposite to the signals on the leads #B, #A, #8, #4, #2, #1. The block 274 checks this and produces an output if they are not. This output passed on lead 275 to the Special Character block 267. Write echo and coder comparison.- The Write Echo outputs of the write circuits, Fig. 8D, indicate what has been written on the tape and are passed over cable 277 to the block 276 in which they are compared with the outputs from the compare coder. If they are not opposite, a signal on lead 279 passes not to the Special Character block 267 but to the EOR character functional block 242. This is because the character is already written on the tape when the check is made so that a special character cannot be substituted for it. The error signal in the EOR block 242 causes the error character E-EOR to be written at the end of the record. In the case of errors detected bv the other three checks, the Special Character block 267 causes a Special Error Character (e.g. " & "). For this purpose the output sockets 281 of the special character block 267 are plug connected to the Write Entry sockets on boards 136 and 154 of the desired character. The erroneous character is suppressed by applying the Clock Gate lead 170 from the Special Character block to the Timing Pulse generator 160 where it cuts the CP1 pulse short. This prevents the erroneous character being placed by the Decoder circuits 134, 140 and the Compare Decoder circuits 150, 152 on the output leads of the corresponding Coders 142 and 156 at the time the Write Sample pulse occurs (i.e. every CP2 time). The Clock Gate lead 170 is also applied to the EOR character block 242 where it causes a positive signal to appear on the E-EOR lead 244 and a negative signal on the N-EOR lead 246. The error signals also pass to the Check Triggers in block 292 where one or more of them may serve to stop the machine as soon as an error is detected as determined by plug connections from sockets 298-301 to one of the stop sockets of block 304. Five channel tape.-Tape punched on the telegraphic code can also be converted, there being provided a Shift Circuit in block 282, Fig. 8B, which is responsive to the Letter and Figure Shift characters on the tape. Figure shift output socket 291 is plug connected to the Decoder input socket 128. All characters after the occurrence of a Figure Shift character are interpreted as figures and all those after a Letter S