And now this???

Invented in 1922 by a professor at Leningrad Electrotechnical University, the reed switch contains two slivers of wire that make contact in the presence of a magnet. Bell Telephone Laboratories evolved this device into the reed relay, in which the switch is controlled by an electromagnet. By the 1960s, reed relays were a fundamental component of telephone exchanges. Their ultralow power consumption also made them popular for space applications, including the Apollo missions.