| 摘要 |
PURPOSE:To prevent the inflow of noise by providing a switch enterring an HPF passing the only outgoing signal, an LPF passing the only incoming signal, and an incoming return signal to the LPF only at the time of the incoming signal transfer. CONSTITUTION:A call signal passes through an HPF 13 of an inflow noise preventing circuit 1 in the outgoing area and a HPF 21 of a CATV converter 2 to be received by a CPU 25. The CPU 25 operates an RF switch 15 to 'pass' it. Then the data bit string is sent to a center device through a MODEM 24. In this case, as this signal is in the frequency of incoming band, it is sent through an LPF 14 to a CATV line 3. In this case, the noise from the other terminal, thereby the inflow of noise to a line 3 is evaded and the inflow noise is prevented. |
