Montgomery County has joined the small but growing list of jurisdictions nationwide offering 9-1-1 services by text message.

The system is not designed for widespread use, officials said, because calling is faster and more accurate. Rather, it is intended for people who have speech or hearing difficulties; in domestic violence or active-shooter situations where speaking might endanger the caller; or when phone service is spotty or not functional.

During a demonstration Monday at the county Emergency Operations Center in Eagleville, advocacy groups said the service could be a game-changer, especially in domestic violence cases.

“I’ve been on that call where the person is calling in a crisis and we say, ‘Is the offender there?’ and there’s the risk of them getting hit,” said Maria Macaluso, executive director of the Women’s Center of Montgomery County. She said the system will also make it safer for service providers like her organization.

“Just in the past few weeks, we had an offender come into our office. I was trying to keep them calm. It would have been wonderful to be able to have been texting police without their knowledge,” she said.

After consulting with the Federal Communications Commission, the four major mobile carriers – Verizon, AT&T, Sprint and T-Mobile – agreed to make 9-1-1 texting available nationwide by May 2014.

But if local dispatch centers aren’t prepared to get texts, the sender gets a bounce-back message. As of last month, nearly 350 jurisdictions were set up, including all of Maine, New Hampshire and Vermont, and most of North Carolina, Indiana and Texas, according to the FCC.

In Pennsylvania, Chester, Allegheny, Dauphin, Lancaster, Lehigh, Washington, Northampton, Lackawanna and Luzerne counties have added the feature. Philadelphia and Bucks counties have said they are working on it.

Since Chester County’s launch in April, Commissioner Terence Farrell said, “We’re not getting a large number of texts, but the ones we have been getting have certainly validated the need for it.”

Chester’s first two texts were about domestic violence, and others came as storms took out cellphone and landline services, Farrell said in an email.

Montgomery officials are trying to notify residents about the service – and what to expect if they use it. On AT&T, there may be a 5-second delay, said Commissioner Josh Shapiro. Dispatchers can send scripted replies (“Where is your emergency?”) or ask specific questions. Sending an address is crucial, Shapiro said, because unlike calls, text messages can be traced only to the closest cellphone tower.

“We don’t want it to become the default, because talking is faster,” said county Commissioner Val Arkoosh. “Absolutely, they should call if they can and text if they must.”