Reed switch can be applied to reed relays. One or more reed switches in a coil reed relay to obtain multiple pairs of pole reed relays. The reed relay operating current is relatively low when used, and provides high operating speed, good performance, which is not reliable switching by the traditional contact, high reliability and long life of very small current. In the 1970s and 1980s, millions of reed relays were used in telephone exchanges. In particular, they were used to switch telephone exchanges for TXEs in the UK. The inert atmosphere around the reed contacts ensures that the contact resistance will not be affected by oxidation. Mercury wetted reed relays are sometimes used, especially in high-speed counting circuits.