While experiment with a high gain transistor it may be noticed the transistor gets saturated by just touching its base. Here is a single, low-cost touch switch based on this idea. The 50Hz hum present in our body is the key of this circuit.BEL BC557B pnp transistor has been chosen for this circuit. All the transistors used in this circuit are of pnp type. The circuit is basically a RS flip-flop
