How to measure time? We often say to wait for me for a while and give me time for a song. How long is the time of which song? By calculating the time and the speed of the tape, use a tape to calculate the time. When the tape rotates, the passage of time can be faintly felt through the frosted glass. The tape stops and the time is over. Disk specifications are: 5, 10, 30 minutes timer keys for play, stop, fast forward