Hughes' Space and Communications (now Boeing Satellite Development Center) built three 376 model satellites, designated Westar IV, V, and VI, for Western Union Telegraph Company. These new spacecraft stand 21.6 feet tall in operation and carry 24 C-band transponders, each of which can accommodate 2400 telephone calls or one color TV channel. The Boeing 376 series of spacecraft uses two telescoping cylindrical solar panels and a folding antenna for compactness during launch. Once the satellite is in synchronous orbit 22,300 miles above the equator, the antenna is erected and the outer solar panel extended, more than doubling the spacecraft's height and power output.