| 摘要 |
PURPOSE:To attain the switching between a normal reproduction head and a still picture head by providing a switching transistor (TR) which controls the bias to the base of a TR of the first stage connected to the still picture reproduction head as well as another TR of the first stage connected to the normal reproduction head. CONSTITUTION:In a normal reproduction mode an H signal is applied to an input terminal 17. Thus both TRs Q5 and Q6 are turned on, and the DC voltage fed back by resistances R6 and R10 is applied to the base of a TRQ1 connected to a head 1. Thus the TRQ1 is turned on, and the reproduction signal is supplied to a following amplifier circuit. In a still picture reproduction, an L signal is applied to the terminal 17 to cut off both TRs Q5 and Q6 with a TRQ7 turned on. Therefore the TRs Q1 and Q2 are turned off and on respectively, and only the still picture reproducing signal is amplified. The normal or still picture signal reproduced by a head switch circuit 14 is switched for every field and extracted as a head amplifier output. Thus it is possible to switch heads with no variation of a resonance point nor a contact defect. |
