This is the design diagram of the trafic baton with bulb flasher circuit. Similar with LED flasher version, the timer NE555 is wired as an astable multivibrator. The “on” period of flashing bulb is around 344 milliseconds and “off” period is around 329 milliseconds. The frequency is around 1.5 Hz. Bulb-driver transistors 2N3053/ BD139 and 2N2905/BD140 are used to light up the lamp. Two diodes are used in series with the base of 2N2905 to increase the forward voltage in order Bto ensure that when BD139 is conducting, BD140 is cut-off. Slide switch S2 is used to change the colour status of the flashing bulb.
In the electrical sector, a schematic diagram is usually used to describe the design or model of equipment. Schematic diagrams are usually utilized for the maintenance and repair of electronic and electromechanical devices / units. Original schematics were made by hand, using standardized templates or pre-printed adhesive symbols, but nowadays Electrical CAD computer software is often used.
In electronic design automation, until the 1980s schematics were virtually the only formal representation for circuits. More lately, using the progress of computer system technology, other representations were introduced and specialized computer languages were developed, because with the explosive development of the complexity of electronic circuits, classic schematics are getting less practical. As an example, hardware description languages are indispensable for contemporary digital circuit design.