| 摘要 |
<p>1347199 Recording digital data EDMAC ASSOCIATES Inc 5 May 1972 [5 May 1971 2 Aug 1971] 21030/72 Heading G4H In a data recording system in which analogue data is converted into binary and then into biphase mark encoded signals which are recorded on magnetic tape, disc or drum, an amplitude detector 42 starts the recorder transport mechanism 66 and alters the clock rate for the A/D converter when the binary signal exceeds a given threshold, e.g. 10% of maximum. In Fig. 1, the outputs of four strain gauge circuits 11, 12, 13, 14 monitoring a motor or a human heart, are amplified, sampled in turn and converted at 18 to 8 bit parallel binary code. Searching is at a fast clock rate until one of the signals exceeds the threshold upon which timer 32 reduces the clock rate to 1/25 the search rate, resets the address counter 30 and frame interval counter 31 and starts the record transport mechanism 66. The frame interval counter controls a selector 38 to accept a frame word from matrix 36 instead of the output from converter 18 at the beginning of each recording period and periodically throughout the recording, for synchronizing during playback. The 8 bit parallel binary signals are converted at 50 to serial form and delayed in a shift register 52 to all the recorder to reach its proper speed to avoid loss of information on start up. The signals are recorded as bi-phase mark encoded signals. The search mode is resumed when no signal has exceeded the threshold in the last 5 seconds. Bi-phase mark decoder.-A decoder for the recorded signals is described with reference to Figs. 2 and 3, not shown. A frequency of 12 times the bit rate is generated by a phaselocked oscillator (III), a divide-by-8 counter is started by each boundary pulse as it arrives and a window pulse is generated from count 4 to count 8, during which the presence or absence of a mark pulse causes a flip-flop to deliver a "1" or "0".</p> |
