| 摘要 |
The primary opto-couplers are phototransistors (4,19) with associated light emitting diodes (5,18). They are driven by control loops (7,22) comprising a differential amplifier connected to another phototransistor (9,24) which is coupled in parallel with a primary phototransistor to its complementary l.e.d.. The impedance modulation circuit (10) associated with the phototransistor (4) for the emission channels (6) produces a signal in phase opposition to the emission signal and divided according to the ratio of the resistors (12). A differential amplifier (16) sums this resultant signal with the received line signal. Other forms of separation are possible such as the Weston bridge. |
