| 摘要 |
PURPOSE:To permit only persons who know a mnemonic code to use a telephone set, by enabling calling only when an input mnemonic code agrees with that in a mnemonic memory part. CONSTITUTION:A mnemonic code, inputted from keyboard 9, is converted by keyboard deciphering circuit 10 into a fixed code, which is sent to CPU16, comparing circuit 12 and control circuit 13. On receiving the signal from circuit 10, circuit 13 sends a control signal to mnemonic code memory part 11. Memory part 11 receives the control signal and sends an internally stored mnemonic code to circuit 12. Circuit 12 compares the mnemonic codes sent from circuit 10 and memory part 11 and, when the two agree mutually, sends a high-level signal to FF14. By receiving this signal, FF14 is set to a high level. The output of FF14 is AND-ed with a signal from terminal 17 showing calling conditions by AND gate 15, whose output is sent to CPU16. When the high-level signal is sent from gate 15, CPU16 provides control operation so that calling will be possible. |
