| 摘要 |
PURPOSE:To make data transmission compatible between a two-wire and a four- wire mode through a one-contact changeover switch by providing a gain control amplifier for level adjustment to the output side of a two-wire/four-wire changeover switch and forming a circuit which switches an unbalanced signal as it is. CONSTITUTION:When data is received from a domestic data center, an unbalanced up data signal is passed through a main attenuator 41, a contact (a) of the changeover switch 37, and gain control amplifier 42 and converted into a balanced signal, which is sent out to balanced lines 31A and 31B through a separator 32. On the other hand, when data from a foreign data center is received, the up data signal is supplied to an output transformer 56 through the main attenuator 41 and a contact (b) of the changeover switch 37 and converted into a balanced signal, which is sent out to balanced lines 48A and 48B. Thus, the amplifier 42 is installed at the output side of the switch 37 and the transformer 56 is used when data from the foreign data center is received to use only one contact for the switch 37. |
