GB783865A - Improvements in or relating to method and apparatus for synchronizing transducer head scanning motion in sound recording and reproducing machines - Google Patents

Abstract

783,865. Magnetic and optical sound reproducing apparatus. DICTAPHONE CORPORATION. June 8, 1955 [June 18, 1954], No. 16444/55. Class 40 (2). A method of synchronizing the scanning operation of a sound recording and reproducing apparatus with the motion of a grooveless type record, comprises advancing the scanning mechanism at a first rate during a first portion of a predetermined amount of motion of the record, and automatically changing to a second rate during the remaining amount of said motion, after which the scan is triggered to the first rate of scan. The method is applicable to magnetic or optical record discs and belts and effects correction of tracking error of the transducer caused by slipping and creeping of the record. In the first embodiment, a magnetic transducer 28 traverses a record belt 10 by means of a lead screw 32 coupled through a friction clutch 46 to driving gear 38. After the transducer has been traversed by one revolution of gear 38, corresponding to an amount somewhat less than a predetermined amount of motion of the record belt 10, a detent 56, forming part of a spring-loaded armature of a relay 30, locks the lead screw 32 against the action of friction clutch 46 until such time that an electrically conducting strip 76 on the record, corresponding to the predetermined amount of motion of the record, reaches stationary contacts 78 which causes a thyratron circuit to be fired to operate the relay 80 and restore drive of the lead screw 32. Fig. 7 shows a record trace 75 on the belt 10, the points B representing a fixed transverse line from which position the drive to the lead screw is restored, and points A representing positions at which the traverse of the transducer is stopped, the longitudinal locations of which vary in accordance with the amount of slip of the record occurring during the last predetermined period. A second embodiment is described in which the lead screw and transducer is stationary and feed of the transducer only occurs during the variable catch-up period, producing a track as illustrated in Fig. 8. Specification 783,866 is referred to.