When used as wayside signals they usually use the following meanings (exact meanings are set by the individual railroad company):

There are no intermediate wayside signals between interlockings: operation is solely by cab signal.

On many of the lines, there are no intermediate wayside signals between the interlockings.

Using a special design allows to reuse the old wayside signals - the transparent data balises are connected to the older distant and stop signals.

Britain generally uses only wayside signals, those posted along the track.

The wayside signals consist of point (switch/turnout) position indicators in proximity to switches and inter-station signalling placed at each station stop.

The TTC subway uses conventional wayside signals without cab signaling.

The line is signalled with advisory wayside signals except on surface portions in street medians or in-street running.

Multiple objectives, including signaling information without wayside signals.

This was, Gates later claimed, when he realized that he did not have a wayside signal to proceed north at Gunpow.