| 摘要 |
PURPOSE:To detect a real speed of a head from both one-phase and two-phase servo-systems, by selecting 'high' and 'low' of a servo-system switching signal. CONSTITUTION:A two-phase differential timing controlling circuit, and a one- phase differential timing controlling circuit are constituted of EOR gates 21a, 21b and a 2-4 decoder 22, and other circuits, respectively. A servo-system switching control signal 33 becomes an H level when operating a one-phase servo-system, and a Q signal of FFs 27a, 27b of the prestage is inputted to AND gates 24e, 24f through NAND gates 26a, 26b. The gates 24e, 24f are in an unable state, therefore, output signals of the gates 26a, 26b pass through the gates 24e, 24f, and signals 36, 39 become switch control signals of a speed detecting circuit of the post-stage as they are. Also, in a two-phase servo-system, the signal 33 becomes an L level, and the decoder 22 becomes an enable state. Accordingly, outputs of the gates 24e, 24f become the same level as an output of the decoder 22, the output signals 36-39 of the decoder 22 become switch control signals of the speed detecting circuit of the post-stage, and a real speed is detected. |
