What are those tiny lights on curling stones?

Published: February 15, 2014, 1:17 am, by Dena Rosenberry

A reader named Jim asked a great question that came to mind while he watched the curling action from Sochi:

What are those tiny lights that blink red or green on top of the curling stones?

It takes a little bit of explanation.

Every sheet of curling ice has two hog lines – stripes that run across the ice sheet 15 feet in front of each house.

Curling sheet diagramIn any curling game, no matter the level of competition, the player delivering a stone must release the stone at or before the near hog line (33 feet from the hack, or starting point, from which the stone is delivered).

In years past, opposing players would watch for their opponents’ “hog line violations.” And at major events, an official would be designated to stand at the hog line and watch for violations.

Technology has brought us electronic sensors that watch for us.

At national and international competitions, an electronic strip is installed at the hog lines when the ice is put in.

Also, the handles on all the stones are replaced with special “sensor” handles.

The special handles have sensors in them (and they feel slightly different to the touch than the handles of other curling stones).

When a player is ready to deliver a stone, you’ll see him or her tilt the rock, which activates the sensor. If you saw a close-up image of the rock right before delivery, you’d see the two tiny green lights blink, letting the player know the sensor is activated.

The player delivers the stone as usual.  If he or she holds onto the stone as it
crosses the hog line, the lights flash red, a hog line violation is called, and the stone is pulled from play.

When the player releases the stone in time, the lights turn green and stay that way as the rock travels down the sheet of ice.

I hope that all makes sense!

Sochi 2014 curling stoneThe sensor handles take a little getting used to at first, but once you get into the routine of using them, it becomes second nature.

In this photo of a stone used in the Sochi Olympics (provided by women’s Team USA vice skip Debbie McCormick), you can see the coating on the handle of the stone and the two small lights (not lit) at the top of the handle near the Olympic rings.

Thanks for your question, Jim!

Please email questions to dena.rosenberry@gazette.com or comment below.

Some folks are simply asking questions on Twitter. I’ll answer them there, too: @djrosenberry