Abstract: The present invention is directed to a motor rotation speed controlling apparatus including a comparator, a detecting circuit for detecting a feedback signal of a motor, a motor driving transistor, and a circuit for changing the level of a constant voltage fed to the comparator. The comparator compares a saw-tooth voltage with a constant voltage and outputs a signal which has a duty cycle corresponding to the result of the comparison. The motor driving transistor drives the motor in response to the output signal from the comparator. To change the duty cycle of the output signal from the comparator, a circuit is used that changes the level of the constant voltage in response to a feedback signal detected by the detecting circuit.

Abstract: A method for producing a glass capillary tube, which comprises drawing under heating a multiple tube assembly comprising a plurality of glass tubes having different diameters arranged coaxially one in another and simultaneously integrating the assembly by heat fusion.

Abstract: A measuring circuit device comprising a measuring circuit, a display associated with the measuring circuit for displaying data generated by the measuring circuit, a display test circuit for testing the display, a performance test circuit associated with the measuring circuit for actuating the measuring circuit to display predetermined reference measured data by the display, a switch for initiating operation of the device, a switch circuit which upon actuation of the switch actuates the display test circuit and the performance test circuit, and which in a predetermined time period, initiates a measuring operation by the measuring circuit.