| 摘要 |
PURPOSE:To carry out data signal extraction tolerant to noises and a dropout by using the output of a filter which extracts a specific frequency component corresponding to the data signal in an FM signal selectively. CONSTITUTION:A level detector 2 detects envelopes of an extracted signal (A). Further, they are compared with a prescribed reference level to obtain a binary level (B). A gate 3 extracts only a real binary level data signal by gate pulses (C) to obtain a data output (D). The gate pulses (C) cut off components in a video signal with the binary level (B). The inserted part of the data signal for a frame number, etc., is predetermined in recording, so it is generated easily by a gate pulse generating circuit. Consequently, even if a noise is superposed upon the data signal part in the FM signal, only a specific-frequency component is extracted through a BPF, so no evil influence of noises is exerted. |
