Abfuehleinrichtung fuer Magnetbandspeicher

888,692. Electric digital-data-storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 31, 1958 [Dec. 31, 1957], No. 42256/58. Class 106 (1). Apparatus for sensing information on a storage medium includes sensing-means for producing electrical signals representing such information, means for converting such signals into unipolar signals and differentiating the latter, means for integrating the differentiated signals and trigger means for providing discrete information pulses from the integrated signals. Information stored in " non-return to zero " form on a storage medium such as a magnetic tape is sensed by a transducer to produce an output waveform A which is fed over a line 10 to a phase inverter 11. The phase inverter produces an output on a line 12 comprising a waveform corresponding to the input waveform A, together with one 180 degrees out of phase with it. These waveforms are fed to a mixing and clipping stage 13 to produce an output waveform B. The waveform B is fed to a differentiator 25, a diode 28 being provided to eliminate negative swing in the output waveform E. The waveform E passes over a line 29 to an amplifier and clamp 30 arranged to shift the reference level of the amplified output below earth potential, as shown in waveform F. The waveform F passes to an integrator 15, a diode 33 blocking positive voltages. The output G of the integrator passes to a Schmidt trigger circuit 21 turned on when the grid potential of the left-hand tube rises above a threshold level and turned off when this potential falls below the threshold level. Each trailing edge of the waveform H corresponds to a binary " 1 " read from the storage medium and the information finally passes to a register 24 where it is effectively in the form illustrated by the waveform J. The function of the differentiator 29 is to obviate the time displacement in the pulses supplied to the register 24 which would otherwise occur. A circuit for the amplifier 30 is described in detail. Specification 875,694 is referred to.