GB1150309A - Improvements in or relating to Magnetic Store Read-Out Arrangements. - Google Patents

Abstract

1,150,309. Frequency and phase modulation recording. SIEMENS A.G. 9 Dec., 1966 [10 Dec., 1965], No. 55238/66. Heading G4C. Frequency or phase modulated information in a magnetic layer store is scanned to produce a reading signal which is evaluated independently of a reference pulse pattern recorded in a separate track, the evaluated signal being employed to form output signal pulses whose positions in time are determined by the reference pulse pattern, the time interval between successive voltage peaks of the reading signal being compared with a measuring time that is up to 70% of the reference pulse interval, and an evaluator pulse shorter than the pulse interval being formed if the distance in time between successive voltage peaks is larger than the measuring time. Binary data recorded on a magnetic tape, plate or drum store in frequency modulated form, i.e. one and two changes of magnetization for 1 and 0 respectively, when read is passed via a band-limiting reading amplifier (not shown), transformer 1 and symmetrical differentiator 2 to a bi-stable trigger 3. The trigger 3 is switched on and off when its input rises above a positive threshold and falls below a negative threshold respectively. The trigger outputs are differentiated and then mixed in an OR gate 4. Each pulse from gate 4 returns a ramp generator 5 to a low value from which it then rises. If the ramp reaches a high value before the next input pulse from gate 4 arrives, the arrival of this pulse produces a pulse from threshold device 6. This pulse sets a trigger 7 which is then reset by the next bit clock pulse from a timing track on the store. This clock pulse also causes a trigger 8 to take up the state trigger 7 had just before the clock pulse arrived. The output of trigger 8 thus represents the data bits 1 and 0 as the presence and absence of constant duration synchronized pulses. The thresholds of the trigger 3 may be automatically adjusted in accordance with the peak voltages encountered, or the reading amplifier may be a control amplifier. It is mentioned that a similar system can be used with phase modulation recording. Input to the store may be from an electronic further store.