Signals start disabled, and enabling one is what starts acquiring it. A trigger on a signal nobody acquires can never fire, so arming a trigger enables its signal for you.

Calibrate in a signal's row menu opens the gain and offset it is currently drawn through, so a trace already scaled by a gain of 2 shows 2 — pressing Apply confirms it rather than resetting it. A signal nobody calibrated shows the identity, 1 and 0.

Calibration is applied at ingest, so changing it re-plans the buffer and drops the history. So does enabling or disabling a signal, and so does a new CONFIG. An empty plot for a second after one of those is the ring refilling, not a fault.

The stream's first signal is usually its timestamp, and that one is never acquired. It cannot be plotted, measured or used as a math source, and udpscope refuses to put it in a row rather than binding a trace that would read nothing for ever.

A signal's colour follows the signal, not the slot, so the same signal on two rows is one colour and the side panel's chip identifies it unambiguously. A signal on no row gets a grey chip rather than none, so the panel's rows keep their height.

Click a coloured chip to change that signal's colour. A grey chip names no trace, so it is not clickable. The colour is saved with the session; Default colour in the signal's ⋯ menu gives the palette entry back.