| 摘要 |
1,177,192. Magnetic tape data stores. R.C.A. CORPORATION. 20 Feb., 1968 [9 March, 1967], No. 8196/68. Heading G4C. [Also in Division H3] A circuit for connection to the monitoring head of a tape recorder to check whether the phase modulated digital data signals have been correctly recorded comprises a pulse discriminator having gating circuits coupled to a balanced signal source and controlled by respective signals produced if the input signals exceed a positive or a negative level for more than a given time. In Fig. 1, the amplified and equilized pulses are applied to a circuit 15 which produces outputs only if the positive or negative signals exceed a threshold level. The output pulses of this are applied to integrators in block 18 and if the pulses exceed a given duration a threshold level is reached which through threshold circuits 21 set a bistable circuit 24 or 25 depending on whether the signal is positive or negative. The input pulse is also applied to a crossover detector 6 the output of which is applied to gating circuits 11 and 12 for positive and negative slope signals respectively, the other inputs of the gates being derived from the bi-stable circuits. An output indicating a correctly recorded signal is thus provided by the gates and this is used to reset a corresponding bi-stable circuit through a line which may include a delay chosen to prevent "race" problems. Fig. 2 shows the threshold detectors and integrators. If the positive going position of a pulse exceeds the threshold of conductivity of transistor 36, transistor 37 is cut off and an integrator capacitor 39 charges. If the pulse subsists sufficiently along the resulting voltage will reach a valve sufficient to switch on transistor 41. This switches off 42 and causes Zener diode 44 and thus transistor 45 to conduct. The lower half of the circuit operates similarly for negative signals diodes 35 and 51 by-passing the irrelevent polarities. |
