Blank Signal Heads on Peek Elite Traffic Signals

[ProfessorJ182]

I've trawled through the forum but could not see a topic/posts which describe these. I've noticed these what look like to be blank signal heads mounted on Peek Elite traffic signals across the UK but never knew what these were for. I've attached a couple of photos of an installation in north Sheffield but I've seen these across the country. Does anybody know what these singular blank looking signal heads are for please?

Screenshot 2024-03-18 111451.png

[matt_12345]

Have a look in this thread:

viewtopic.php?t=43151

[ProfessorJ182]

Thank you.