Sunnyvale police officers said for several days last week they were unable to communicate with their dispatch operators.
NBC Bay Area was told the system is now back up and running, but frustrated officers with the Sunnyvale Department of Public Safety on Monday sounded the alarm.
"I personally experienced having my radio sign called out by dispatch," said David Meinhardt with the Sunnyvale Public Safety Officers Association. "We did not hear them, and finally on the fifth time it did go through."
Police said the problem was intermittent over a 48-hour period -- beat cops could not hear dispatch and dispatchers could not hear officers.
"Imagine even at a school if there had been an active shooter and we can't communicate with one another to help mitigate that problem," Meinhardt said.
For safety, the department assigned two officers per patrol car to make sure each officer had instant backup. But it also delayed response times because fewer cruisers were on the street.
"It's always frustrating when something doesn't go the way you're expecting to go or the way you're trained to use a piece of equipment," Sunnyvale DPS Capt. Jeff Hunter said. "We take that very seriously."
The glitch also affected the fire department.
After troubleshooting, administrators discovered the outage was likely caused by an off-site human error at the agency that runs the communications system.
Employees were testing new equipment meant to allow different police departments to communicate each other. But after the testing, an employee forgot to reset the system to the original settings.
Officer said they want assurances this will not happen again.
"Not having radio communication is of paramount importance," Meinhardt said. "Our safety and the safety of the public of Sunnyvale and those who visit this city is what we're here to do for those folks. It should be scary for everyone."
The police chief told NBC Bay Area he is waiting for a final report on the error from a local joint power authority, which operates the communication system.