Patent GB-1170570-A (GB)
Title: Data Signal Generating Apparatus
IPC: H04L17/02
Filed: 1968-07-31
Abstract: 1,170,570. Keyboard code generators. SCM. CORP. 31 July, 1968 [31 July; 1967], No. 36506/68. Heading G4H. Apparatus for generating binary code data signals each signal being composed of a predetermined combination of bits comprises a set of memory devices serving as output means, a keyboard having a plurality of signal keys 12, Fig. 3, and two special keys, each key 12 serving to operate predetermined ones of a group of switches to provide a signal and means responsive to the operation of a selected key 12 and one of the special keys for sequentially operating certain ones of the group of switches and thereafter a second switch to operate the memory devices to provide a signal distinct from the signal which would be provided by operating only the selected key 12. The signal keys 12 are mounted for vertical movement and each operates a corresponding bar 25 urged upwardly by springs. A series of parallel code bars 26-33 underneath the bars 25 have coded notches 35. Bar 34 has no notch. Switches 36-44 are operated by corresponding bars the others. Keys 13 and 14, Fig. 1, operate switches 45, 46. Depression of a key 12 alone causes one signal, e.g. " 6," to be generated. If key 13 is also depressed, another signal, e.g. " 8," is generated instead. Key 14 in combination with other keys causes machine function signals, e.g. form feed and form separator. The switches 36-43 are connected to memory devices 16-23, Fig. 1, through gates 49. When the switches 36-43 are closed the leads 47 are earthed; transient effects being damped by capacitors 48. The memory stages each consist of a bi-stable comprising two transistors. The closure of switch 44 passes a signal via delay 52 to initiate a 240 microsecond delay 55 which gives a signal on lead 57 to reset all the memory devices 16-23. The transistors Q1 are now on, so that mark lead 51 is at ground potential and space lead 50 is negative. The output 56 from delay 52 is also applied to a lock device 58 energizing a solenoid to lock the keyboard and preventing further keys 12 being depressed. At the end of the 25 millisecond period of delay 52 a pulse is applied over lead 65 to gates 49 to set the memory devices according to the key operated. After 1 millisecond the delay 66 gives a signal on lead 67 connected to diodes 68, 69, 70. If key 13 is depressed, diodes 73, 74, 75 are disconnected from earth and a signal is applied from lead 67 to leads 76 and 82. Similarly, depression of key 14 causes signals to be applied to leads 77 and 82. If both keys 13 26-34. When a key is depressed its bar 25 operates a combination of code bars 26-33 and bar 34 and the corresponding switches 36-44 close. Switch 44 closes slightly after and 14 are depressed transistor Q3 conducts and holds line 82 at earth potential. The effect of pressing key 13 with one of the keys 12 is to change the states of memory devices 20 and 23 thereby altering the output pattern. Pressing key 14 with any key 12 alters devices 21 and 23, and if both keys 13 and 14 are pressed memory devices 20 and 22 are changed. The switch 43 which is connected to memory device 23 is for a parity bit, the coding bars being designed so that the number of " 1 " bits is always the same and remains the same even when keys 13 and 14 are pressed.