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 railgun projectile can reach several times the speed of sound faster than a missile, so it can reach out to the horizon and hit a cruise missile much faster and further away from the ship. Projectiles are also cheaper and smaller, allowing for many more to be carried.