Alternating flasher

The proposed circuit is intended for use by modellers at railway cross- ings, work in progress, advertising boards, and many others. It can be built quite quickly from but a handful of components. In the accompanying diagram, Al determines the flashing frequency, which may be altered by changing the values of R2 and, particularly, R3. The latter may be replaced by a suitable preset if the frequency needs to be varied often. Inverters A2 and A3 function as fixed delay elements, while A4 inverts the drive to D2. The alternately flashing LEDs may, of course, be of any colour suited to the application. 41....A4 = IC1= 7400 alternating flasher 57 R Kambach 86430 •see text