| 摘要 |
A sampling gate of a TDM telephone system, designed to connect a subscriber station to a trunk line during an allocated time slot, comprises a pair of bucking transistors of the same conductivity type (NPN) inserted between a live wire from the station and a corresponding "hot" conductor of the trunk line whose "cold" conductor, tied to the reference wire of the subscriber line, is grounded through an elevated resistance. During the allocated time slot, the two bucking transistors are rendered conductive by a timing pulse applied across their base/emitter circuits via a transformer while a connection leading from their bases to negative biasing potential is temporarily severed by an interposed FET which is cut off by the timing pulse applied to its gate electrode via a differentiation circuit.
|
