AT&T subscribers living in Allegheny County, Pennsylvania can now text to 911 in an emergency situation if calling isn't an option.

AT&T, the second largest wireless carrier in the US, has finally decided to support the niche text-to-911 service in Allegheny County, Pennsylvania. The latest move puts all four major carriers, including Verizon, Sprint and T-Mobile, in support of the new service. AT&T customers can now report emergencies by sending a text message to 911, a move which was approved by the US Federal Communications Commission this month.

Verizon, America's largest wireless carrier, debuted the text-to-911 service in the county in May. Later, T-Mobile and Sprint joined Verizon in offering the service in Allegheny County. Alvin Henderson, head of the county's emergency services, said that the county has received 153 emergency texts since then, according to Post-Gazette.

FCC's approval to the text-to-911 service came after a 3-2 vote and is seen as a complement to the existing calling service and not a replacement. The service is not widely available and requires emergency callers to use it when there is absolutely no resort to make a voice call to 911. The service is helpful for people with speech disability or those who are deaf. Nonetheless, voice call to 911 is deemed a better option to report emergencies, since it gets easier for respondents to probe and understand the issue at hand.

If users find the need to use text-to-911, they must make sure the location and the nature of emergency is mentioned in plain text. Using messaging slang makes it difficult to identify the problem, lest help is delayed. The service isn't available if the user is roaming and does not support attachments such as images and documents, according to the county's FAQs.

A separate report from KSN.com revealed that the service is in its early stages in Sedgwick County with an aim to have all the technology and hardware in place for use by next year.