The concentrated range extender with gain (CREG) provides the subscriber telephone with voice frequency gain, signaling and supervision range extension, and increased loop current so that customer loops beyond the standard central office range can be served. CREG circuits, called 7A REG's, are shared among many customer lines by being connected inside the concentrating portion of an ESS switching machine. Such sharing realizes a typical three-to-one cost advantage over standard per-line treatment. Autonomous operation of the 7A REG minimizes the impact on call processing in the ESS machines, but results in a moderately complex circuit. To satisfy cost and size requirements the 7A REG design uses custom integrated circuits, low profile transformer and relays, and computercontrolled production testing. The 7A REG circuits are configured two on a card. Three hundred twenty 7A REG circuits (160 cards) mount in a standard 7 ft ESS bay together with a control panel, peripheral decoders (in No. 2/2B ESS), and dual -78 V power supplies. A twelve-to-one reduction in effective circuit volume is achieved over earlier nonconcentrated circuits due to the concentration ratio and smaller physical size.