TDAS systems collect data in one of two modes, circular buffer or recorder mode. In circular buffer the status line is active hi, 5V, when the system is armed AND the units are collecting data waiting for a T0 signal. In recorder mode, the status line only goes to 5V when the systems have been armed AND a start record signal is received. In both modes, when a T0 signal is received, the status line goes low (0V). The status line is a common to all DAS in the chain, if any unit in the chain detects a fault when armed it will pull the whole line low (0V).