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闲置的电话线引诱设计者把它的48V电位用作电源。但是,美国联邦通信委员会的电信规定第68章规定:连到电话线并且不使用于通信的任何设备的电阻都不得低于5M
An idle phone line entices the designer to use its 48V potential as a power source. However, Chapter 68 of the FTC’s telecommunications regulations states that the electrical resistance of any equipment connected to a telephone line and not used for communications shall be at least 5M