Abstract: The present invention provides a steam room of a foamed resin molding machine that is superior in terms of heat insulation property and durability, a foamed resin molding machine, and a method for molding a foamed resin. At least one of frames, back plates and center plates that together constitute steam rooms of a foamed resin molding machine are made of foamed aluminum. Alternatively, foamed aluminum plates are laminated onto the frames or the back plates are constituted into a sandwiched structure that incorporates interposed foamed aluminum plates, respectively. The foamed aluminum is advantageous in that its high heat insulation property prevents waste in thermal energy of steam, and other merits include reductions in cycle times.

Abstract: In order to prevent generation of a trapezoidal signal waveform due to limitations on dynamic ranges in an echo canceller and an echo path as voice signal transmission paths, a voice signal processing circuit of the voice signal processing system processes a waveform such that its signal level falls within the narrowest dynamic range without causing an overshoot and waveform crack. Process of a signal waveform is selectively conducted only of a waveform of a voice signal whose signal level is high to be liable to have distortion. As to a voice signal whose signal level is low and originally within a dynamic range, the signal is transmitted without having its waveform processed.

Abstract: In order to prevent generation of a trapezoidal signal waveform due to limitations on dynamic ranges in an echo canceller and an echo path as voice signal transmission paths, a voice signal processing circuit of the voice signal processing system processes a waveform such that its signal level falls within the narrowest dynamic range without causing an overshoot and waveform crack. Process of a signal waveform is selectively conducted only of a waveform of a voice signal whose signal level is high to be liable to have distortion. As to a voice signal whose signal level is low and originally within a dynamic range, the signal is transmitted without having its waveform processed.

Abstract: The invention provides a time division multiplexing system for a digital exchange which suppresses appearance of a time slot which, although exchanging can be performed by a time division switch, is put into a non-used state to improve the efficiency in use and which allows line interface apparatus to be accommodated in a time division multiplexing highway even where the line interface apparatus require a multiplicity larger than that of the highway to suppress an increase in circuit scale and simplify the circuit construction.