System for controlling positions of record tracks relative to a scanning trace of a head device by use of two envelope output signal envelope samplings during a scanning trace

摘要

A system is provided for controlling positions of record tracks relative to a scanning trace of a head device. An envelope detector detects an envelope of an output from a head device operative to scan a record tape along a scanning path transverse to record tracks. A pulse generator produces two pulses appearing respectively at predetermined time points in a period of a scanning trace of the head device. A level sampler samples a level of a detection output from the envelope detector with the pulses produced by the pulse generator to produce two sampled outputs. An improper position detector detects improper positioning of a group of record tracks traversed by the head device relative to the scanning trace of the head device based on a difference between the sampled outputs from the level sampler. A tape controller adjusts a travelling speed of the record tape to control positions of the record tracks traversed by the head device relative to the scanning trace of the head device in response to a detection output from the improper position detecting circuit.