Visitors attending Supreme Court arguments surrender their electronics on entering the courtroom. So if something rings, chimes or buzzes, it's likely the device's owner is dressed in a black robe.

Last year, a justice's cellphone went off. But last month, when four electronic pings sounded during an argument, the device was different. It belonged to Justice Sonia Sotomayor and was alerting the justice, who is diabetic, that her blood sugar was urgently low.

The 63-year-old justice has had diabetes since childhood, but the sound was the first public notice that she was using a continuous glucose monitor.

Sotomayor's use of the device doesn't indicate a change in her health, experts told The Associated Press, but it does show her embracing a technology that has become more popular with Type 1 diabetics.

In 2013, when Sotomayor did an interview with the American Diabetes Association's "Diabetes Forecast," the magazine reported she was not using one. But in recent years the devices, which use sensors inserted under the skin, have become more accurate, said Cleveland Clinic endocrinologist Kevin Pantalone.

Monitors give users continuous information about glucose levels, rather than the snapshot they get from testing their blood with a finger prick. Information from the sensor gets sent every few minutes to a device where a user can see it charted. Most devices sound alarms at low and high glucose levels. Some monitors work with an insulin pump, which continuously delivers insulin.

It's not clear when Sotomayor began using the technology. She declined comment through a court spokeswoman. But the dinging during arguments on March 21 followed an incident in January where emergency medical personnel treated her at home for symptoms of low blood sugar.

Aaron Kowalski, an expert in diabetes technologies, said an event like that can prompt a person to try a monitor, but even people using the devices can experience low blood sugar that might result in an emergency call. Kowalski, who leads the research and advocacy efforts of JDRF, the Type 1 diabetes research organization, said about 15 percent to 20 percent of Type 1 diabetics now use such a device.