PURPOSE: To detect a bias current most suitable for magnetic recording medium automatically in a short time, by detecting the bias current when difference between maximum reproduction output levels reaches a prescribed value.
CONSTITUTION: A test signal f1 from a generator 16 is intermittently picked up under the control of a CPU9, recorded on a tape 8 with a head 7 for R channel via a switching circuit 3, a sensitivity adjusting device 4 and a frequency characteristic adjusting device 5, reproduced at a head 10 and applied to a 3% distortion detector 19, where the signals f1 and 3f1 are compared, and the output level is switched and given to the CPU9 when both are made equal. When the signal f1 A/D-converted 25 is received by the CPU9, a signal f2 is generated from the generator 16 for recording and reproduction in the similar way. The bias current is controlled so that the difference between bias currents based on the signals f1, f2 can be directed to a value corresponding to the optimum recording bias current, allowing to obtain the optimum recording bias current for a tape in use.
| JPS59104702 | HIGH-SPEED COPYING DEVICE |
TANAKA YOSHIAKI
OOTSUKI YOSHIKI
MOURI TOMOHIRO
HASEGAWA AKIO
