| 摘要 |
1,264,444. Radio receiving circuits; transistor amplifying circuits. BLAUPUNKT-WERKE G.m.b.H. 19 Nov., 1970 [19 Nov., 1969], No. 55079/70. Headings H3Q and H3T. A coupling circuit for passing a television video signal from a first unit 10, Fig. 1, to a second unit 11 at video frequency while isolating the chassis of the two units from each other comprises a transformer 13 having a primary winding 14 and a secondary winding 15 and switching means 19, 22, respectively, for connecting the primary winding 14 with the first unit 10 and the secondary winding 15 with the second unit 11 during the picture signals to pass them to the second unit 15 the picture signals, and for disconnecting the windings from the units to enable the stored magnetic energy of the transformer to be dissipated in a shunt 16 during the line synchronizing intervals. In an embodiment, a television receiver comprises a video detector feeding into an emitter-follower (not shown) coupled to the primary winding 35, Fig. 3, of transformer 36 via cascaded emitterfollowers 32, 34. The secondary winding 37 feeds the input of a video tape recorder via emitter-follower 38; the resistive shunt 35 is connected across primary winding 35. The switching means comprise the collector to emitter paths of transistors 43, 40, the bases of which are driven from windings 46 on the transformer of a blocking oscillator 45; the -base of this is supplied with line flyback pulses over capacitor 47. The emitter of transistor 40 is coupled to the emitter of an auxiliary transistor 41. A channel for playback of recorded video signals is also provided, and this comprises transformer 60, having a primary damping resistor 62; transistors 68, 69 with their bases driven from the windings 46 comprises the switches. Recorded video signals are applied to the primary winding 62 via cascaded emitter followers 52, 57, 59, transistors 52, 57 being A.C. coupled by capacitor 55 and the D.C. restored by diode 53. The output from secondary winding 63 is transferred to the television receiver via an amplifier comprising emitterfollower 64, a grounded base stage 65 and output stage 67. |
