| 摘要 |
A number of pairs of, e.g., yellow (19) and red (2) LEDs arranged in a conventional pattern are selectively actuated to define a character display, etc. The LEDs in each pair are respectively drivable by a DC source (21) via circuits including NO switches (15,16) that are closed when respective transistors (13,14) conduct. The conduction timing of one transistor (13) is controlled by output from an ambient light sensor (2) supplied via a voltage control oscillator (4) and a monomultivibrator (6). The other transistor (14) is controlled by output of an AND gate (11) receiving one input for the monomultivibrator (6) and one input from a detector (8) which produces output only when the light sensor (2) output is above a set level. |
