| 摘要 |
The system makes possible that the trunk circuit of private switch board holds jointly a D.C. by-pass circuit, a transformer impedence matching and gain control circuit by using the analog switch. It also provides the circuits that controls the voice communications and facsimile's transmissions and receptions. It comprises a PCM code (14), a CPU (15) for the system control, a the switching control circuit (16) for the first and second switching signal, a fax modem (17), a reception gain setting circuit (18), a transmission gain setting circuit (19), and analog switchs (20,21,22) switched by the 1st and 2nd switching signal.
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