| 摘要 |
PURPOSE:To reduce the number of information lines, by transmitting column information and row information of a key matrix from an attendant switchboard to a switch board in a time-division mode. CONSTITUTION:Scanning pulses of key matrix 1 are being sent out from scanning control circuit 6 via column counter 4 and row counter 5. An operator turning ON any key, the output signal of counter 4 is decoded 2, applied as a column selective pulse to multiplexer 3 via the cross point, and returned to circuit 6 as row information. When the row information pulse is received, circuit 6 actuates transmission control circuit 9 at the same time when setting the value of counter 5 to units-digit transmission circuit 7 and the value of counter 4 to tens- digit transmission circuit 8. Consequently, the key information of matrix 1 is transmitted to the switchboard as a two-digit dial number. |
