Abstract: A telephone terminal executes voice communication with a partner telephone terminal by using a selected codec program to code and decode voice signals. Both telephone terminals have facilities for storing codec programs and transferring codec programs over a communication network. During a voice call, one of the two telephone terminals may transfer a codec program to the other telephone terminal, and the call may then proceed by use of the transferred codec program. This enables voice communication to take place with the best codec program that either telephone terminal can provide, even if the two telephone terminals are associated with different communication systems.

Abstract: A tension leveler includes a work roll coming into contact with a metal sheet and a pair of backup rolls coming into contact with the work roll. A hardening layer harder than the inside of the backup rolls is formed on the surfaces of the backup rolls. The Shore hardness inside the backup rolls is lower than the Shore hardness in the surfaces of the backup rolls by HS23 to HS36.

Abstract: A telephone terminal executes voice communication with a partner telephone terminal by using a selected codec program to code and decode voice signals. Both telephone terminals have facilities for storing codec programs and transferring codec programs over a communication network. During a voice call, one of the two telephone terminals may transfer a codec program to the other telephone terminal, and the call may then proceed by use of the transferred codec program. This enables voice communication to take place with the best codec program that either telephone terminal can provide, even if the two telephone terminals are associated with different communication systems.

Abstract: A clean room is adapted to provide a plurality of clean air zones with different degrees of cleanliness. Air is passed through high efficiency particulate air filters in the ceiling of the room and withdrawn through shutters in the floor of the room. The shutters are adjustable to maintain a pressure-balanced system. The room is divided by walls and partitions to define different zones which are filtered by different classes of filters depending on the degree of cleanliness required in each zone.