Patent GB-768183-A (GB)
Title: Timing and clocking circuits for data processing machines
IPC: G11B20/16
Filed: 1955-02-04
Abstract: 768,183. Digital electric calculating apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Feb. 4, 1955 [Feb. 8, 1954], No. 3342/55. Class 106 (1). A timing device for a data processing machine comprises a source of timing pulses, cyclical pulse distributing means having a cycle time equal to the time space between adjacent pulses, means for generating a signal on the completion of each distributer cycle, and means for producing an error indication if a signal occurs in the absence of a timing pulse or if a timing pulse occurs without a signal. In the described embodiment the timing pulses are derived from a magnetic drum 150, Fig. lb. Each of the five sectors S1 to S5 is divided into ten " words " which are subdivided into digit values as indicated in Fig. 18. Signals indicating the beginning of each word are derived from a track 152 and, after passing via line 155, buffer diode 158, and lines 159, 161, are applied to a double inverter 163. This device, shown in detail in Fig. 12, assumes two states of conduction according to the input voltages applied to it. The input signal at 162 changes it to the second state and an output from 164 is passed through a pair of cathode-follower amplifiers 166/168 and 169/171 to provide a positive output signal at a terminal DGX. The signal is also applied to a diode 174 of a gate 176, the other diode 175 of Which in common with corresponding diodes 229 &c. of gates 211, 234.... 238, 243, is normally subjected to a positive voltage and therefore provides a positive output on line 178, via buffer diode 203 and line 161 to maintain the positive input at terminal 162 of the device 163. Negative timing pulses are derived from a track 151 of the drum 150 at times indicated by the vertical lines in Fig. 18. Just before the digit " 0 " time, therefore, a negative pulse is transmitted via line 154 and briefly closes the gate 176, thus removing the positive bias momentarily from the input terminal 162 of the double inverter 163. The resulting negative pulse from terminal 215 drives the second double inverter 212 to its second state and this, in turn, sends a positive signal via a pair of cathode-follower amplifiers 221/222 and 223/225 to provide a positive output signal at a terminal DG0 and also a positive input to the diode gate 211 which opens when the negative timing pulse from track 151 terminates and provides a positive latching voltage at the input 232 of the device 212 until the next negative timing pulse arrives. In this manner the openended ring of two-state devices 163, 212, 235, &c. is stepped on until the double inverter 244 of the DG10 stage is returned to its first state upon the arrival of a negative pulse from the track 151 at the gate 243. This event should coincide with the arrival of another positive pulse from the track 152 signalling the beginning of the next word period. As the device 244 returns to its first state an output from terminal 247 tends to change over a further double inverter 249 and so produce a positive output signal at terminal 251 of the latter. The arrival of the pulse signalling the beginning of the next word would have a similar effect on the device 249, being transmitted via line 155, diode 252, and line 254 to the input 255. However, suitably amplified versions of the positive output from terminal 256 of the DG10 device 244 and the positive beginning-of-word pulse from track 152, are applied to a further diode gate 263, and the output from this gate nullifies the signal from the terminal 251 which would otherwise operate error devices including a neon indicator 291.