For laying indoors , intunnel or cable trench, unable to bear external mechan-icalforces. Single-core cable in magnetic duct is not permissible.
室内、隧道及电缆沟等场所，不能承受机械外力。单芯电缆不允许敷设在磁性管道中。
2
Mechan-ics model, basic formulas , basic measures and an example to use the method are given, which is significative in theory and applicable in engineering.
提出了该方法的力学模型、基本公式、基本方法和算例。具有理论意义和工程应用价值。
3
The author deals mainly with the principle of the mechan- amplifier and the design, selection and method of use of digital circuit and photo-resistance circuit.