The Design of a Machine for High-Speed Duplication of Video Records

Instead of reproducing video records by re-recording from the master tape at the normal playback speed, a faster method is accomplished by the process of magnetic transfer. The video master is recorded on a high-coercivity tape, which is then held in contact with an unmagnetized tape of low coercivity while both tapes are passed through a magnetic bias field. If tape coercivities and bias field strength are properly chosen, a mirror image of the master recording is transferred to the previously unmagnetized tape, without erasing the master. Since video recordings contain wavelengths as small as 2.5 μm, any separation or slip between the two tapes during transfer can result in an incomplete or distorted reproduction of the master recording. In the magnetic transfer device described here, the tapes are clamped together by means of compressed air, which maintains good contact between the tapes during transfer. With this experimental machine, high-density video information can be transferred at high speeds, producing copies of uniformly good quality. Copies with a SNR of 42 dB have been made consistently at speeds up to 150 in/s, which would make it possible to copy a one-hour video program in three minutes. The mechanical design of the magnetic transfer device is described, and experimental results are reported.

Print ISSN

0361-4573

Published

1969-09

Content type

Original Research

DOI

10.5594/J10810