Abstract: A playback error associated with overwriting on a narrow-width track is prevented from occurring in the overwritten portion. A signal generator (11) generates a signal of a predetermined data pattern that stabilizes the operation of a synchronizing pulse generator of a playback system (shown in a separate figure). A timing generator (4) switches over a switch (12) to the output of the signal generator (11), at least a period of time equivalent to writing of one track before the main signal is input. When a signal of the predetermined data pattern from the signal generator (11) has been output, the timing generator (4) switches over the switch (12) to the main signal. The playback system includes a circuit which discriminates between the predetermined data pattern and the main signal data from a playback signal generated by playing back a record on a magnetic tape (T).

Abstract: A playback error associated with overwriting on a narrow-width track is prevented from occurring in the overwritten portion. A signal generator (11) generates a signal of a predetermined data pattern that stabilizes the operation of a synchronizing pulse generator of a playback system (shown in a separate figure). A timing generator (4) switches over a switch (12) to the output of the signal generator (11), at least a period of time equivalent to writing of one track before the main signal is input. When a signal of the predetermined data pattern from the signal generator (11) has been output, the timing generator (4) switches over the switch (12) to the main signal. The playback system includes a circuit which discriminates between the predetermined data pattern and the main signal data from a playback signal generated by playing back a record on a magnetic tape (T).

Abstract: An annular valve seat comprises an annular elastic seat member of large width formed in its outer periphery with a circumferential groove having an enlarged bottom and a trapezoidal cross section, and an annular metal core substantially conforming to the groove in cross section and fitting in the groove. The seat is fitted to the inner surface of the case of the valve defining a flow passage. When the valve is installed in a piping system with pipe flanges fitting to the valve case at the opposite ends of its flow passage, the opposed pipe flange surfaces hold the opposite side faces of the valve seat in pressing contact therewith to tightly fit the seat to the case. The disk of the valve has stem holding bores each provided with cutouts extending inward axially thereof and also circumferentially of the disk at the upper end of the bore to permit escape of air from the bore.

Abstract: A collapsible lever device comprising a main lever mounted on a valve stem extending from the main body of a valve and an auxiliary lever pivoted to the forward end of the main lever. The main lever and the auxiliary lever are provided at the pivoted portion with a lower plate and a contact plate respectively for holding the auxiliary lever in alignment with the main lever. When the auxiliary lever is turned to its unfolded position in alignment with the main lever, the levers provide a single elongated lever. The valve main body has a cover covering the base end of the main lever from above and provided on the edge thereof on the main lever side with an engaging portion in the form of rack grooves, pins or teeth. The auxiliary lever is formed on its upper surface with a pawl engageable with the engaging portion of the cover. A grip lever having a hook at its one end is mounted on the auxiliary lever.