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This undated photo shows a rotary dial telephone. (Dan Hardy/Houston Chronicle via AP)

Practice makes perfect. 

Six months after state officials recommended callers in Colorado’s 719 and 970 area codes start getting in the habit of dialing 10 digits — area code plus phone number — for all local calls, the change became official on Sunday.

The switch is to make way for 988, a three-digit dialing code to reach the National Suicide Prevention Hotline, slated to go into effect on July 16.

The change to 10-digit dialing applies nationwide and is intended to prevent callers from accidentally calling the suicide hotline when dialing local numbers with a 988 prefix, according to the Colorado Public Utilities Commission. 

When 988 takes effect, it will function like other state and national three-digit numbers, including 911 (of course), but also 211, which in Colorado reaches Mile High United Way, to connect people in need with community services, 811, a hotline to locate underground utility lines before digging, and 311, a number many cities, including Denver, use to link residents with information.

Colorado Crisis Line: A statewide hotline. 1-844-493-8255, or text TALK to 38255.

It’s unknown how many customers will be affected by the change to 10-digit dialing in Colorado because local telecom service providers do not report data to the state by area code, said James Cullen, a spokesman for the Department of Regulatory Agencies, which oversees the PUC.

The change applies to both landlines and cell phones, Cullen said.

Brian Heersink, the IT director for San Luis Valley Health in Alamosa, in the 719 area code, said the hospital updated the system that manages 1,200 phone extensions to 10-digit dialing a few years ago.

“It’s just been a good practice in my field for a while,” Heersink said.

Aside from changing how callers dial, officials recommend making sure all other devices that use phone numbers be reprogrammed to 10-digit numbers, as seven-digit numbers will no longer connect. 

Affected devices could include life safety systems or medical monitoring devices, fire or burglar alarms, security systems and gates, speed dialers, phone contact lists, call forwarding, voice mail, fax machines, and the last few folks using dial-up internet numbers. 

How many dial-up customers remain in Colorado wasn’t immediately available, though at least one company — called — appears to still offer dial-up internet plans in Colorado. All of its dial-up connection numbers use 10 digits.

The move is the latest in a long history of area code and dialing changes in Colorado, according to the Colorado Virtual Library. 

The 303 area code was first established in 1947, and covered the entire state until 1988, when a growing population necessitated the creation of the 719 area code for southern Colorado. In 1995, the 970 area code was added to cover northeastern and western Colorado. 

By 1998, even the Denver area was running out of 303 numbers, and the 720 area code was added, mandating 10-digit dialing for all local calls since the two area codes overlapped. Colorado has one more change to the phone network on the horizon. Beginning in April, new phone customers in the Denver metro area may be assigned a new area code, 983, intended to provide enough new phone numbers for the next 25 years.

An early 1900s file photo shows the interior of the Mountain States Telephone and Telegraph Company switchboard office in Grand Junction. Telephone customers in the 970 area code, which includes Grand Junction, now must dial 10 digits instead of seven to make a call. (AP Photo/Mountain States Telephone & Telegraph Co.)

David is a former Colorado Sun staff writer.

Twitter: @davidgilbert4u