GB821580A - Improvements in or relating to sound transducing apparatus - Google Patents

Abstract

821,580. Dictating-machines. ELECTRIC & MUSICAL INDUSTRIES Ltd. April 14, 1958 [April 13, 1957], No. 12123/57. Class 40 (2). A dictating machine backspacing mechanism in which the backspacing movement is stopped when the transducer reaches the point where the dictated passage began. The mechanism is for use with a disc record machine in which the inward traverse of the transducer is produced by a spirally grooved guide disc in the centre of the turntable, engaged by a toothed wheel which is rotated by an electromagnet to achieve backspacing which is initiated by closing a switch 6 in circuit with a relay 8 which has holding contacts 9. A D.C. supply is provided at the terminals 7. Relay 8 closes contacts 10 in circuit with the coil 5 and in series with the cam-operated contacts 11, so that a series of impulses are transmitted to coil 5 and through a pawl associated with the toothed wheel effects backspacing. The arm 4 carries a bracket 13 in which slides a toothed rod 14 which is normally spring-urged away from the centre of the turntable, but is prevented from moving by a second pawl, which can be withdrawn by energizing a coil 15. The coil 15 is energized by closing a switch 22 which energizes a relay 21 and closes the contacts 23 which energizes a relay 19 through the normally closed contacts 18 of the switch 16. The relay 19 has contacts 24 in circuit with the coil 15 and hence when the relay 19 is energized the member 14 is released and moves outwardly until it opens the contacts 18 and is locked by the second pawl. Backspacing is then limited to the point where the member 14 engages the switch 16, opens the contacts thereof and de-energizes the relay 8. Specifications 697,161 and 819,996, [Group XL (a)], are referred to.