At 1:30 a.m. Sunday, police and fire dispatchers noticed that messages from officers were being cut short. At times, they said, transmissions were inaudible.
Also, with the police system, calls from one police district in Kensington were migrating to a citywide band.
Public safety officials said the problems were intermittent but not resolved until 15 hours later, at 4:30 p.m.
"Our members feel they can't rely on this system," said David Kearney, a paramedic and representative for the firefighters' union, Local 22 of the International Association of Fire Fighters. "Firefighters are just waiting for something to go horribly wrong."
Steve Gorecki, a Motorola spokesman at headquarters in Schaumburg, Ill., near Chicago, said the problem was caused by a faulty piece of hardware - a "timer card" that fits into a dispatcher's console and controls the clarity of audio.
"This was a hardware problem," Gorecki said. "It's rare for something like this to take place."
Just Thursday, Motorola executives testified before City Council that they were paying extra attention to the Philadelphia system and monitoring it nonstop by computer from corporate headquarters.
But on Sunday, it was police dispatchers - and not Motorola technicians based in either Philadelphia or Schaumburg - who detected the problem.
Given all of Motorola's assurances, city officials angrily questioned why Motorola wasn't the first one to pick up on problems Sunday.
"Motorola didn't tell us; we told them," said Deputy Police Commissioner Charles Brennan. "We're befuddled why it took them so long to track down the problem."
Motorola's Gorecki said there was no alarm capable of picking up the intermittent audio problems that were caused by a hardware problem.
Motorola's digital radio system that operates on the 800 megahertz band of radio frequency spectrum is used widely by public safety agencies across the country. At Thursday's City Council hearing on radio problems, Tom O'Drain, president of Local 22 of the firefighters' union, said firefighters in Chicago, New York, Los Angeles and Washington have also complained about the Motorola system.
In Philadelphia, problems began to surface this year. The Police Department has reported at least four episodes of interrupted radio coverage, while the Fire Department has received increasing complaints from the field about blocked radio transmissions.
"It's been one thing after another," said Philip R. Goldsmith, the city managing director. While he characterized the Motorola digital system as "far superior" to the old radios used by fire and police, he said the persistent problems are untenable.
"With any new system, you expect the occasional glitch, but you want to make sure that for $54 million you're getting your money's worth," he said.
"I have serious concerns about the reliability of the system," Goldsmith said.
Since the Fire Department switched to the Motorola radios in October 2002, it has received 50 complaints from fire commanders about communication problems at fire scenes; 20 of those reports have been filed in the last three months.
Consultants are studying whether interference from cell-phone transmissions could be part of the problem. Some cell-phone carriers such as Nextel operate on radio frequencies next to public-safety channels.
But there are issues, too, with the Motorola system itself.
Joseph James, the city's deputy commissioner for public property, said yesterday that city officials have confirmed that firefighters had radio problems at a Port Richmond house fire on Aug. 20 that killed two firefighters.
He said firefighters at the scene experienced trouble getting calls out because they were sending encrypted messages over clear channels.
He also confirmed yesterday that there were problems with the "hot mike" feature that is supposed to immediately open a microphone for a firefighter in distress for 10 seconds. The Fire Department disclosed Thursday to City Council that there was no evidence that the hot mike worked for the two firefighters who died.
"The hot mike didn't work; we know that for a fact," James said. "Motorola is working to come up with a fix."
In the face of continuing radio problems, the City Controller's Office is launching an audit of the city's contract with Motorola Inc.
Councilman Frank Rizzo, who cosponsored the hearings in City Council, questioned why the city was paying Motorola $1.5 million a year to maintain the system. "It's not acceptable to pay maintenance on a system that doesn't work well," Rizzo said.
