The city has reached an agreement to allow the Franklin Institute to convert a sign on the Benjamin Franklin Parkway to digital, officials said Monday.

The street-level sign is at 20th Street and the Benjamin Franklin Parkway and is used to promote the museum's exhibits.

The proposed conversion has been criticized since the institute applied for a permit in 2012 to update the sign. Opponents argued that allowing a digital sign would negatively impact the Parkway.

"This agreement in no way means there will be more electronic signage on the Parkway," Managing Director Michael DiBerardinis said in a statement.

"The arrangement protects the Parkway and doesn't turn it into the Las Vegas Strip," DeBerardinis said. "More importantly, the city has formulated new regulations to prohibit such signage elsewhere on the Parkway going forward."

Under the agreement between the city and the museum, the content of the digital sign cannot change more frequently than every 30 seconds and is limited to "programs, exhibits, features, and activities of the Franklin Institute."

The sign, which is 128.5 inches and 68 inches tall and 48 inches off the ground, must be turned off between 10 p.m. and 6 a.m. daily.

In consultation with the city, the museum must limit the brightness of the sign and equip it with an automatic light sensor to adjust its brightness.

The museum cannot use strobe lights, flashing messages or images, or scrolling messages.

"We see the converted sign as an effective and innovative way to communicate in real time the many programs and offerings the Franklin Institute provides to the public," said Larry Dubinski, president and CEO.

"One can only assume that Ben Franklin would be proud of our use of modern technology to showcase the ways in which we uphold the mission of the Franklin Institute," Dubinski said.

The Zoning Board of Adjustment granted the museum a variance for the sign, but that decision was challenged in court by Scenic Philadelphia, which advocates against outdoor advertising, and the Logan Square Neighborhood Association.

A Common Pleas Court judge dismissed the case in 2014, saying the plaintiffs lacked legal standing, and Commonwealth Court dismissed their appeal last year.