Patent GB-1258321-A (GB)
IPC: G06K7/10
Filed: 1969-03-13
Abstract: 1,258,321. Label readers. MONARCH MARKING SYSTEM CO. 13 March, 1969 [19 Sept., 1968 (2)], No. 13368/69. Heading G4M. [Also in Division G1] In an arrangement for sensing code marks arranged in a circular track on a label or the like by means of a rotating scanning head, n times as many clock pulses as there are bit positions in the track are generated in each revolution of the scanning head, and a counter which is started in response to sensing a start mark on the label causes sampling of the scanning head output at every nth pulse. Scanning head, Fig. 4.-A motor 103 rotates a disc 188 carrying photodetectors 97, 98 for sensing the code and start marks respectively, illumination of the label being provided by a lamp 183 and optical fibres 190. The detector supply and output leads 125-127 are connected to external circuits by way of slip rings 129-131. Rotating with the head is a slotted opaque disc 81 having an associated lamp 76 and detector 78 for generating the clock pulses. The spring-biased probe 12 for engagement with a central aligning hole in the label has an associated switch which is actuated when the probe is in the retracted position. Circuit, Figs. 10A, 10B.-The probe switch 165 when actuated energizes motor 103 and lamps 183, 76, and removes the system reset signals provided by circuit 371. If the associated equipment e.g. a cash register or D.P.A. is ready to receive data, detection of the start mark sets flip-flop 214 so that clock pulses (20 per code position) are passed by gates 219, 223 to a divide by 2 Î 10 counter 233, 234 for the period in which the start mark is detected so that, at the end of this period, counter 234 holds a number corresponding to half the width of the start mark and enables a corresponding one of gates 251 to 258. The clock pulses are also fed for a complete scanning cycle to a decode counter 238 having outputs connected to  gates 251 to 258 so that the selected one of these gates is enabled twice in every code mark scanning period. A divide by two flip-flop 240 is driven by counter 238 and inhibits every other output from NOR gate 262 at gate 260 to provide sampling pulses at the approximate mid point of each code mark pulse. The code pulses are entered in a register having its stages 271- 275 enabled in turn by a ring counter 315-319 driven by a stepping circuit 320 connected to outputs of counter 238. When a complete character has been entered in the register, circuit 340 causes read-out from the register and samples the state of a parity check circuit 350 to which the sampled code pulses are applied over line 261. A parity error produces a system reset signal. Read-out of each character advances a counter 361 so that end of message circuit 360, in conjunction with sensing of the start mark for the second time, sets a flip-flop 381 to light an indicator lamp on the scanning head as well as providing a system reset signal. Removal of the probe from the label de-energizes the motor and the lamps. Modified circuit, Figs. 13A, 13B (not shown). -Every other clock pulse is fed to a counter while the start mark is being sensed, and thereafter all clock pulses are counted to provide sampling pulses at the mid points of the code marks, these sampling pulses being applied as a shift input to a shift register to which the code pulses are fed. When each character has been entered, it is gated out in parallel by a shift register marker pulse initially inserted in the first stage. Similar end of message and parity check circuits to those mentioned above are also provided.