At night signal lamps could be used for a similar purpose.

A signal lamp winked from a tree on the ridge line.

He was being signaled by someone on the beach with a signal lamp.

Stop arms and signal lamps must be disabled or removed.

When a calling party lifted the receiver, a signal lamp near the jack would light.

The vanes on the signal lamp flipped up and down again.

Several minutes passed; then he saw the reassuring beam of a signal lamp that flashed three times.

Naval ships often use signal lamps and Morse code in a similar way.

And this was why we almost missed seeing the transmitter's green signal lamp, which lit up as before.

But at the, moment he had other things to do and then I saw that the signal lamp wasn't on any more.