| 摘要 |
The amount of recording time remaining on a partially recorded videotape cassette (11) is measured by fixing the position of a body member (17, 117) relative to the hub (14) of a cassette reel, and moving a pointer (24, 120) to point to the outermost layer (33) of tape (12) wrapped around the hub (14). Movement of the pointer relative to the body member causes corresponding movement of an index (38, 145) relative to a time scale (39, 125), so that the remaining time can be read off the scale. The pointer is coupled so that small movement of the pointer relative to the body member, causes large movement of the index relative to the scale. In one embodiment, a transparent disc pointer (17) is coaxially attached to a transparent disc body member (24). Disc (24) is rotated to position the point of intersection of a spiral line (34) on disc (24) with a radial line (23) on disc (17) above the outermost layer (33) of the tape, causing corresponding rotation of a radial line (41) on disc (24) relative to a time scale (39) annularly located on disc (17).
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