| 摘要 |
PURPOSE:To detect the magnetic tape remaining time before a tape is driven by revolutions of both supply and take-up reels in the same direction, by detecting different rotational frequencies of the supply reel owing to the number of turns of the tape to the supply reel and calculating the tape remaining time before the tape loading state is ended. CONSTITUTION:A disk 22 having a slit is attached coaxially to a rotary shaft 4 of a reel drive disk for a supply reel 2. At the same time, an LED24 is set above the disk 22 and a photointerrupter 23 consisting of a phototransistor 25 is provided under the disk 22. The supply reel drive disk is revolved for a period from the start to the end of tape loading, and the pulses detected by the interrupter 23 are supplied to a counter 26 through the slit of the disk 22 which is revolved coaxially with the shaft 4. The counter 26 counts the pulse number (n) generated in response to the revolutions of the disk 22. This counted pulse number (n) is fed to an arithmetic part 28 to obtain the tape remaining time T shown by an equation [ I ]. |
