GB1224574A - Improvements in or relating to recording systems for business machines - Google Patents

Abstract

1,224,574. Selective signalling. DIGITRONICS CORP. 29 July, 1969, No. 38088/69. Heading G4H. A business, e.g. adding, machine having character and function keys is associated with a system for recording signals representing the characters entered and the functions performed in response to operation of the keys, and to ensure correct recording even in the event of incorrect key operation, a signal generator is connected to key-operated switches to produce corresponding signals for recording only when a key has been fully operated, and the generator removes its output in response to an acknowledgement signal from the recording system when the character signals have been recorded. As a key is depressed, it first actuates a mechanical interlock and sequentially opens and closes magnetic reed switches 110, 80 respectively, switch 80 only being closed when the machine is mechanically committed, i.e. when the operated key has set a mechanical memory element on a carriage and the carriage has been advanced to a position intermediate two successive character-storing positions. Closure of switch 80 connects the output of transistor 28 to switches 114 which are selectively operated by the character keys, and in response to the output on leads 118, the recording system produces and stores character code signals. The transistor bi-stable circuit is set over lead 93 in response to the acknowledgement signal to remove the output from transistor 82. The bi-stable cannot be reset until switch 110 has closed, which occurs when the key has been released and has passed beyond the point at which the carriage has completed its step to the next character-storing position, so that multiple machine entry and recording by a "dithering" keystroke is avoided. Signals representing the functions performed by the machine are generated by switches associated with the function keys, the signals only being produced on closure of a switch by a cam when the machine has been committed to the performance of the selected function.