By Andria Borba

SAN FRANCISCO (CBS SF) — Intercom companies are scrambling to update systems in dozens of buildings around San Francisco now that the dialing procedure for the 415 area code has changed.

“San Francisco was caught off guard,” Mark Greenspun of AAA Intercom Systems told KPIX 5.

READ MORE: DA's Office: Man Shot Dead By Daly City Police Was Wielding Fake Gun

The new 628 area code means all calls within the 415 must dial eleven digits, adding a “1-415” to existing numbers to buzz open the doors of San Francisco apartment buildings.

READ MORE: Prosecutors: San Jose Flooring Company Owner Charged With Wage Theft; Workers Owed Nearly $1M In Overtime

The fix takes about an hour, and in the Tenderloin neighborhood alone there are some blocks with 20 now useless buzzers.

MORE NEWS: State Lawmakers Vote Down Bill That Would Phase Out Fracking In California

“I had a building with 150 tenants and it took two of us two and a half hours to reprogram it,” Greenspun said.