This circuit will help you to control two devices with the help of a switch. If you “on” the first device then second device remain “off”, and if you “on” the second [[wysiwyg_imageupload::]]device the first device will become “off”. Therefore you can control both the devices with the help of single switch. The circuit is built around CD4017 which is a CMOS decade counter/ Divider. Used in many applications like binary counter/decoder, frequency division, divide by N counting, Alarm system etc. CD4017 is a 16 pin IC which includes 3 input- Clock, Reset and Clock inhibit. And 10 output Q0- Q9. Pin 16 is for power supply and pin 8 is used for ground. Read more to find out working of the circuit.

SPDT stands for Single Pole Double Throw. It comes with 6 pin. It has 2 states ON and ON. For instance if we have two devices a red LED and a blue LED then SPDT switch will turn ON red in one position and blue in other position. By making different connections of the pins the two ON states can be made of same polarity or opposite polarity. Hence, it will switch ON a different device in each position. Hence, it is also known as changeover switch. This switch has found applications in industry, etc.