Why doesn t a music tape machine play a note when it s on pause in the same way that a VCR generates a picture when videotape is on pause Are the machines so very different

A.� VCR’s and audio tape players work on a similar principle. In both machines a magnetised tape moves past the playback head that picks up the changes in the tapes magnetic field. A signal is generated by the resulting fluctuating electric field, which pushes a current through a coiled wire. Finally the current generates an audio signal, for the tape machine, and video and audio signals in the VCR.

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Q.� So why the difference in the way 'pause' works

A.� Because of the one major difference between an audio tape player and a VCR. In an audiotape machine the playback head is fixed whereas a VCR's playback head spins.

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So, when you pause an audiotape machine neither the tape nor the head are moving and so no signals are picked up. However although a video tape stops on moving one pause the VCR playback head is still spinning and so picks up the changing magnetic fields and fluctuating electric fields needed to produce the video and audio signals. That's why you can still see the image from a paused VCR on your TV screen.

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Q.� Doesn't this wear the VCR heads out

A.� It would actually wear out the tape and this is why most VCR's stop pausing after around 5 minutes.

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Q.� Why doesn't any sound come from the VCR when the tape is paused

A.� Because a muting device prevents any unwanted sound.

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Q.� Why the difference

A.� Practicality probably. A static image on your TV screen is useful, whereas a single note from an audiotape wouldn't give you enough information to tell you where you had paused the tape. It would also be rather annoying.

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by Lisa Cardy