It’s taken a long time for Clay Cantrell to get to flip “the switch.”

Like hundreds of other engineers at television stations across the nation, he finally will pull the plug on analog transmitters and go all digital Friday.

“As far as for me, it’s really just going up there and shutting off the analog and throwing the switch,” said Mr. Cantrell, senior engineer at WTVC NewsChannel 9.

Preparing to flip that switch has not been so quick and simple.

The transition began in the mid- 1990s, when Congress decided the change to digital needed to be made to free up part of the broadcast spectrum for emergency communications, according to the Federal Communications Commission. The date for the switch originally was Feb. 17, but lawmakers made a last-minute decision to extend the deadline to Friday.

Locally, WTCI, WDEF, WFLI and WDSI all changed to a digital signal at or before the February deadline, but Mr. Cantrell’s Channel 9 and WRCB-TV Channel 3 decided to wait until the revised deadline. Nationally, 756 stations had made the switch as of Wednesday, leaving 1,030 to go all digital by Friday.

“I think really that having two dates worked well,” said Tom Tolar, president and general manager for WRCB. He explained that the dual deadlines forced consumers to realize what the switch meant while still having a “lifeline” from the other two stations that didn’t change.

“It probably gave the viewers a little more time to get acclimated to the new system,” Mr. Cantrell said.

Some affected consumers, Mr. Tolar said, probably will not buy the converter boxes until their screens go completely dark.

“Quite frankly at this point I think no matter what date you set there would be a small number of people still unprepared,” he said.

But industry studies show more people are prepared now than were prepared at the original date.

A study by the National Association of Broadcasters showed 82 percent of affected households were ready in April, compared to only 51 percent ready in January.

In a news release, the association’s Vice President for DTV Transition Jonathan Collegio said the numbers represent a “dramatic acceleration in preparedness.”

“Almost everyone knows about the transition now,” he said. “By and large, the only folks left may simply be procrastinating or may believe the date might change again.”

The FCC has said several times in recent releases that the deadline is not expected to change again.