The present invention provides two subscriber line testing systems, three broadband/narrowband telecommunication systems and a broadband line card. In the subscriber line testing systems of the present invention, a test module is configured in the CO broadband device, reducing the complexity and the cost of the subscriber line testing systems. In the broadband line card provided by the present invention, line capturing relays are configured in the broadband line card so that the LPF card can be designed as a passive device to reduce corresponding costs, thus using this broadband line card helps reduce the complexity of the CO broadband device and the subscriber cost thereof. In the three broadband/narrowband telecommunication systems provided by the present invention, by using the subscriber line testing systems and the broadband line card, the complexity of broadband/narrowband telecommunication systems and subscriber cost thereof are also reduced. In the third broadband/narrowband telecommunication system provided by the present invention, both the broadband line card without line capturing relay and the broadband line card with line capturing relay can be incorporated so that a better compatibility is provided.