A method and apparatus is provided for DC feed control for a line card. Messages may then be selectively transmitted to the user. Each of the master data lines extends in a space between one of the port pads and a respective one of the memory arrays. The release system is operable to open the closed compartment in response to the output signal of the control. Based on the measurement, a bias control feedback loop directs a variable voltage generator to adjust a bias voltage applied to the APDs such that a difference between a voltage of a break-down pulse and a preselected logic voltage level is minimized.