Abstract: A method of diametrically contracting a cylindrical body, includes the steps of grasping the cylindrical body with a plurality of elongated grasping members, preparing a cylindrical drawing die having an opening at one end and a tapered inside peripheral surface, drawing the grasping members together with the cylindrical body into the drawing die, through the opening, and applying a compression force to the cylindrical body through the grasping members due to the passage along through the tapered inside peripheral surface, to thereby cause the cylindrical body to be diametrically contracted. During the drawing process, since the cylindrical body does not come into direct contact with the drawing die, neither scratches nor baking cracks are produced on the outside surface of the cylindrical body.

Abstract: A click tone removing system for a time division switching system which performs switching of speech channels by a highway switch inserted in a highway. When a hook information detector and a dial information detector detect hook information and a dial information, respectively, delivery of a PCM speech sending signal to the highway is prevented by a blocking function for a fixed period of time, so that the highway is controlled to switch the speech channel, thereby removing a click tone generated by dialing.

Abstract: A channel switching network, in which each cross-point of a switch matrix is constituted as a channel switch of balanced type using two PNPN semiconductor elements. Each of the two PNPN semiconductor elements is arranged in a forward direction with respect to a direct current flowing from the channel switching network to a corresponding terminal equipment. A column of cross-points and a line of cross-points in the switch matrix are designated to select a simultaneously designated cross-point in response to a pair of selection signals. A control circuit is provided for each pair of the incoming lines and the outgoing lines of the switch matrix so that the terminal voltage of a power source for flowing the direct current in the PNPN elements is controlled to temporarily rise to turn ON the PNPN elements at the selected cross-point and thereafter to drop to such a value as only to maintain the PNPN elements in the ON states.