| 摘要 |
1,083,417. Trigger circuits. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 26, 1965 [Sept. 16, 1964], No. 36761/65. Heading H3T. [Also in Divisions B6, Gl and G4] A circuit producing a signal at an output terminal 80 if the light impinging on a photo-cell 13 exceeds a certain adjustable value, comprises four transistors 55, 60, 66, 73 connected so that the current produced by the cell 13 when the reflected light exceeds that value, causes the transistors 55, 60 to be cut off, thus placing the base 65 of transistor 66 at earth potential and causing transistors 66, 73 to be fully conductive so that a signal is produced at the terminal 80. The collector 68 of the transistor 66 is connected to the base of transistor 55 through a feed-back resistor 71 so as to apply a latch-back voltage. With the voltage developed by the cell 13 below a certain value, transistors 55, 60 are fully conductive causing base 65 of transistor 66 to become negative, thus cutting off both transistors 66, 73. An adjustable potentiometer 46 connected to the junction of cell 13 and base lead 54 is set to determine the light level at which a signal is produced. A diode 53 between the junction and the cell 13 prevents damage to the transistor 55 if the cell 13 fails. |
