JPS5522287A - Automatic optimum record bias detector - Google Patents

Abstract

PURPOSE:To secure an easy and accurate setting of the optimum bias value of the magnetic tape with every tape by detecting the variation state of the reproduction output when the bias current is increased or decreased in steps. CONSTITUTION:The electric signals of a fixed level and fixed frequency are generated from record signal generation circuit 10; while the bias current varying in steps is produced from record bias current generation circuit 11. These electric signals and the bias current are recorded on magnetic tape 5 through record head 6 and then immediately detected by reproduction head 7. And this reproduction output is converted into the digital signals to be compared with just preceding value at comparator 15 with every increment of the bias current by one step. Then the bias current value when the reproduction output has no increment even with increment of the bias current at certain several steps plus the bias current value when the reproduction output has no increment even with decrement of the bias current at certain several steps are memorized in holder circuits 16 and 17. These relative increment average are calculated by adder 18 and divider 19 to obtain the optimum bias value.