| 摘要 |
PURPOSE:To decrease the number of component parts and at the same time reduce the attenuation quantity of a call signal caused by a capacitor, by putting a semiconductor switch having a combined self-supporting function between a subscriber terminal and a current supply circuit of a trunk. CONSTITUTION:Semiconductor switches D1 and D3 having a self-supporting function are cut off with switches D0, D2, D4 and D5 conducting respectively when a call mode is secured between the SUB.A and SUB.B. Accordingly a talking is possible between the SUB.A and SUB.B via C0 and C1 since DC surrent is supplied to both the SUB.A and SUB.B. The SC0 and then switches D0, D2, D4 and D5 are cut off, and SC0 plus D1 and D3 are actuated at the next instant. Thus DC current route of E0-SUB.A-E0 is formed. Under these conditions, D0 and D4 are cut off with an AC-like separation given between the SUB.A and SUB.B to realize a privacy mode. |
