Abstract: A D/A conversion circuit with a small area is provided. In the D/A conversion circuit, according to a digital signal transmitted from address lines of an address decoder, one of four gradation voltage lines is selected. A circuit including two N-channel TFTs is connected in series to a circuit including two P-channel TFT, and a circuit including the circuits connected in series to each other is connected in parallel to each of the gradation voltage lines. Further, an arrangement of the circuit including the two N-channel TFTs and the circuit including the two P-channel TFTs is reversed for every gradation voltage line. By this, the crossings of wiring lines in the D/A conversion circuit becomes small and the area can be made small.

Abstract: The music roll perforating system permits a paper music roll to be perforated from a special previously prepared magnetic tape containing a digital recording of a music rendition. The process and apparatus disclosed uses a small computer to drive a music roll perforator through a driver box. The driver box accepts a serial data stream from the computer and converts it into parallel channels with high current/high voltage outputs capable of driving the solenoids used in a conventional music roll perforating machine.A magnetic tape recorder is attached to the computer for the dual purpose of either loading a computer program into the computer following turn-on or for reading the specially prepared digital recording into a computer memory. A Teletype machine is also attached to the computer to permit input to the computer from an operator.