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小型煤矿用的多路电话系统——杰姆斯R·敏斯等2人;116—123 这是一种新型的电话系统,可在一根扭绞屏蔽电话线上提供8对双工通讯通道,而无需中央交换台或线路放大器。该系统的安装和维护比采用一般交换系统简单得
Multi-line telephone system for small coal mines - 2 people, James R Mens; 116-123 This is a new type of telephone system that provides 8 pairs of duplex communication channels on a twisted shielded telephone line Without the need for a central switching station or line amplifier. The installation and maintenance of the system is simpler than using a common switching system