TAPE VELOCITY DETECTOR

• US 3,805,286 A
• Filed: 02/01/1973
• Issued: 04/16/1974
• Est. Priority Date: 02/01/1973
• Status: Expired due to Term

• Current Assignee: Thomas S. Kavanagh, William H. Bunker
• Original Assignee: Thomas S. Kavanagh, William H. Bunker
• Inventors: Kavanagh, Thomas S., Bunker, William H.
• Primary Examiner(s): Konick, Bernard
• Assistant Examiner(s): Levy, Stewart
• Application Number:
  US05/328,730
• Time in Patent Office: 439 Days
• Field of Search: 340/174.1A,174.1B 178/6.6P 179/1.2S 235/92DN
• US Class Current: 360/51
• CPC Class Codes: G01P 3/60 by measuring or comparing frequency of generated currents or voltages frequency comparators H03K5/26
• CPC Class Codes: G11B 15/46 Controlling, regulating, or indicating speed dependent on position of tape in reserve, loop G11B15/56, G11B15/58
• CPC Class Codes: G11B 15/52 by using signals recorded on, or derived from, record carrier
• CPC Class Codes: G11B 15/54 by stroboscope; by tachometer
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/13 the information being derived from movement of the record carrier, e.g. using tachometer

Abstract

In a magnetic recording and playback system a detector indicates the velocity of the magnetic tape. The number of data bits read back in a given interval of time is compared with a preset number. If the number of data bits counted exceeds the preset number, it is an indication of slippage between the capstan and magnetic tape. A tachometer generates tachometer pulses related to the speed of the capstan. Data bits read back between successive tachometer pulses decrement a counter which is preset at the beginning of each tachometer period with a given count. If the counter is decremented through zero during any tachometer period, a signal indicating possible tape slippage (tape velocity slow) is produced. The number of counts remaining in the counter at the end of each interval is compared with another preset number to determine whether the tape velocity is too high.

Claims

1. In a magnetic recording and playback system in which bits are recorded on and played back from magnetic tape, said system including means for recording bits on said magnetic tape, means for reading the recorded bits and a capstan for driving said tape past said means for recording and means for reading, a detector for indicating the velocity of said magnetic tape comprising:

a tachometer connected to said capstan, said tachometer producing tachometer pulses spaced in time, and having a period between pulses, varying in relation to the speed of said capstan, a counter for counting said bits, means for controlling said counter in response to said tachometer pulses so that the count in said counter represents the total number of said bits received by said counter within said tachometer pulse period, a comparator for comparing the number of bits counted in said time intervals with a preset number, and means for generating a velocity error signal when said number is outside of a given range.

2. The system recited in claim 1 wherein said counter is a decrementing counter, means to preset said counter to a given count on successive tachometer pulses, means for decrementing said counter by one count for each bit in each of said time intervals, and means for generating a velocity error signal representing tape slippage when said counter is counted through zero during any interval.

3. The detector recited in claim 2 further comprising:

means for generating a signal representing a predetermined count, and means for comparing the count remaining in said decrementing counter at the end of each interval with said predetermined count, said comparator producing an error signal if the count remaining in saiD counter is greater than said predetermined count.