GB842336A - Improvements in or relating to tape record apparatus - Google Patents

Abstract

842,336. Magnetic recording and reproducing apparatus. MINNEAPOLIS-HONEYWELL REGULATOR CO. May 7, 1957 [May 7, 1956], No. 14513/57. Class 40 (2). In a tape record apparatus information is recorded in a series of discrete blocks spaced along the tape and interlaced with blocks of another series. The invention is particularly applicable for a data processing machine or computer in which information is required to be spaced in discrete blocks along the length of the tape and is frequently required a single block at a time. When a magnetic tape is used a high relative velocity between tape and transducer is required, resulting in unused lengths of tape between each block to cover the accelerations of the tape between its operative velocity and the stationary positions. The invention utilizes these spaces and adjusts their length by recorded pulses to enable a separate series of blocks to be recorded thereon. In the embodiment described with reference to Figs. 2 and 3, the second series comprises the second half of a recording sequence, when the tape drive has been reversed. Thus 25,000 blocks may be recorded in each direction, Fig. 2. Fig. 3 illustrates a magnetic marking system which permits the apparatus controlling the tape to sense the particular blocks of a desired series, to sense the logical half-way point, i.e. the physical end of the tape, as well as when the tape has been rewound back to the starting-point. The markings take the form of recorded signal tracks B, E for each half of the record and may conveniently be separate channels. Track B comprises an initial signal producing a positivenegative-positive combination of pulses, as shown in Fig. 3, C, to indicate the start of block 1, which is then terminated by a negative pulse. The following blocks are similarly indicated by positive and negative pulses to represent respectively the start and finish of the blocks. It is sometimes desirable to read the tape in the reverse direction, and it will be seen by the present system, as indicated in Fig. 3, D, that the signals still produce a positive pulse at the start of a block and a negative at the end. At the physical end of the tape, i.e. the logical middle, a special signal 44 will produce an alternating pulse 45 which conditions the apparatus for recording and reproducing the second logical half of the tape, so that during the return movement the start and finish of each of the blocks 25,000 and onwards will again be represented by positive and negative pulses, respectively, as shown in Fig. 3, G. Fig. 3, F, represents the signal produced by the reverse drive of the tape. A special signal 47 at the end of the second logical half reconditions the apparatus for the start of a forward drive. Electronic control circuits are described, with reference to Figs. 4 to 10 (not shown), whereby the pulses effect the conditioning of the circuits of the recording and reproducing apparatus.