Abstract: The upper frame 3 and a pair of the side frames 5 in the frame body 2 are simultaneously formed by bending the first frame plate 20 which is obtained from a raw flat plate by pressing treatment. And the upper frame 3 is formed into a pipe form having a slit 6 with edge portions and the slit 6 is welded at four positions corresponding to the bending portions 3B and the concave portions 9 in the horizontal portion 3C, thereby the slit connecting portions 10 are formed. Accordingly, based on that main members for constructing the seat back frame 1 are formed from the first flat frame plate 20, number of the members for constructing the seat back frame 1 and process number for assembling thereof can be easily reduced.

Abstract: An integrated service network ("ISDN") is structured to connect subscriber lines through a packet switching system to incoming or outgoing packet switching calls without passing them through a circuit switching system. This effectively uses the speech path of the circuit switching section instead of using it for packet switching calls. At the same time, the invention minimizes the influence of the introduction of the ISDN upon the software of the circuit switching section. The ISDN digital switching network applies to circuit switching calls which are switched at a local switch and to packet switching calls which are to be switched at a toll switch.