Double switching or double cutting is the practice of using a multipole switch to close or open both the positive and negative sides of a DC electrical circuit, or both the hot and neutral sides of an AC circuit. This technique is used to prevent shock hazard in electric devices connected with unpolarised AC power plugs and sockets. Double switching is a crucial safety engineering practice in railway signalling, wherein it is used to ensure that a single false feed of current to a relay is unlikely to cause a wrong side failure. It is an example of using redundancy to increase safety and reduce the likelihood of failure, analogous to double insulation. Double switching increases the cost and complexity of systems in which it is employed, for example by extra relay contacts and extra relays, so the technique is applied selectively where it can provide a cost-effective safety improvement.
Read more about Double Switching: Railway Couplings
Famous quotes containing the word double:
“What happens is that, as with drugs, he needs a stronger shot each time, and women are just women. The consumption of one woman is the consumption of all. You can’t double the dose.”
—Ian Fleming (1908–1964)