Abstract: A subscriber line tester for communication lines that convey high speed digital data, wherein a transmission side tester is provided that divides a measuring frequency region into two or more blocks, generates multi-sine waveforms obtained by combining sine waveforms of two or more frequencies in each block, and outputs the multi-sine waveforms to the communication line; and a reception side tester is provided that measures the multi-sine waveforms in the most suitable range for each block, and synthesizes a spectrum from each spectrum obtained for each block, so that high speed communication and long time period measurement are improved.

Abstract: An electronic circuit module, having a small total thickness and excellent heat dissipation efficiency, and comprising insulating containers for holding electronic components therein and arranged between a thin metal board and a printed circuit board; surface contact connectors mounted between first planar surface contact terminals formed in the containers, and second planar surface contact formed on the printed circuit board, to make electrical connections therebetween; and securing means for securing the surface contact connectors to the metal board so that the connectors are lightly pressed between each container and printed circuit board. Pipes are disposed in the metal board for carrying coolant therein. Thus, heat generated by the electronic components is conveyed to the board via the containers, and hence to the outside for dissipation. The foregoing structure is advantageous in reducing the thickness of the module substantially, and in increasing the heat dissipation efficiency.