Two lamps connected in series with an open switch ... Two lamps connected in parallel with an open switch and a cell The circuit diagram shows a circuit with two lamps connected in parallel.

The circuit ... 2.2 K resistor in parallel with the LEDs. When turned on by the PIC, this transistor causes roughly a 10 mA current to flow through the Zener diode and its series resistor.

A parallel circuit ... connected in big circuits but you can switch individual devices off, without affecting the others. Because, unlike a simple string of lights in a series circuit, these ...