English: The first induction coil, built by Irish scientist and Catholic priest Nicholas Callan in 1836 at St. Patrick's College, Maynooth, Ireland. It is still preserved by the college. It consisted of a horseshoe-shaped piece of iron with two windings of wire around it, a short winding and a long winding. Callan found that when he sent pulses of electricity from a battery through the short winding, higher voltage pulses were produced by the longer winding. This was the first step-up transformer, and with it Callan discovered the principle that the voltage ratio in a transformer is equal to the turns ratio.