Plain old telephone service. For direct inward dialing service, the telephone company provides one or more trunk lines to the customer for connection to the customer's PBX, and allocates a range of telephone numbers to the customer. Calls to such numbers are forwarded to the customer's PBX via the trunks.
A railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor. railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (at the end connected to the power supply), it completes the circuit.
A spin-off manga entitled A Certain Scientific Railgun and a corresponding anime adaptation has been released, centering on Academy City's 3rd Level 5, Mikoto Misaka, and the daily life in Academy City. A certain Fan Translation project for the light novels can be found here.