Signal level indication with different colors

摘要

A signal level indicator comprises first and second voltage comparators responsive to the low and high levels of an input signal, respectively. First and second switching transistors are provided. The base of the first transistor is connected to the output of the first comparator through a first diode, the base of the second transistor being connected directly to the output of the second comparator. First and second light-emitting diodes which emit different colors are respectively energized in response to the conduction of the first and second transistors. The collector of the second transistor is further connected to the cathode of the first diode through a second diode to cause the first diode to switch off to thereby turn off the first transistor in response to the turn-on of the second transistor.