Before he was in charge of McLean County's emergency dispatch center, Tony Cannon was a Normal police officer who occasionally had some fun with dispatchers back at post.

"As long as it was a non-emergency situation, and time wasn't an issue, I would throw out some police radio 10-code that wasn't commonly used just to try to throw them off," Cannon said.

Then and now, all emergency dispatchers have a list of the codes available but it's seldom needed. The 10-codes, as they're called, use a prefix of "10" attached to another number to provide a numeric shorthand to describe an action. A code of 10-70, for instance, means fire.

"Our dispatchers and emergency personnel tend to use the more common 10-codes regularly because the last thing we want is any confusion," Cannon said. "If it's not a commonly used 10-code, we use plain language."

In December 2006, the National Incident Management System, part of FEMA, established guidelines to discontinue the use of 10-codes in multi-agency, multi-jurisdiction and multi-discipline events such as major disasters and exercises. It did not, however, discourage the use of 10-codes in everyday department communications.

"We use a limited number of the codes for communication within our own department," said Bloomington Police communications coordinator Darren Wolf. "Those are the ones everyone is familiar with and knows by memory. But if another agency is working with us, it's plain language. It comes down to common sense. If there is even a question, always go with plain language."

The codes were developed in 1937 by Charles Hopper, the communications director with the Illinois State Police. Police radios bore little resemblance to the high-tech equipment of today and speech times were limited. Hopper saw a need to abbreviate radio transmissions for police officers.

The use of 10-codes hit pop culture in the 1970s when CB radios were common. DeWitt County 911 coordinator Tony Harris said it is not unusual to hear law enforcement officials use 10-codes in everyday conversation.

"We have discussed the use of 10-codes a few times in our department," Harris said. "But if it is outside your department, you have to assume they may not know those codes."

There's a part of Harris that hopes 10-codes always will be around in some form or another.

"It's our lingo," he said. "We use 10-codes all of the time in conversation around the department. Sometimes, I even use it at home and my wife will remind me that I'm not at work anymore."

Dan Fulscher, Logan County Emergency Management Agency director, said Logan County is moving away from using 10-codes, and always when other departments are involved.

"Our policy is that when you have local, state or federal mutual aid with any situation, you use plain language," Fulscher said. "It can lead to confusion in a time when you can not allow for any confusion."

Fulscher learned his lesson during a training exercise when a health department official reminded him he was using 10-codes without explanation.

"I remember being told that 'Roger' was a person's name, not an acknowledgement of something," Fulscher said.

Departments sometimes use the codes so radio transmissions don't alarm the public, Cannon said. For instance, while everyone may understand what 10-4 means, chances are most people don't know the code for someone with a gun (10-32).

"There are just certain times when you want to use a little more discretion but something like that can alert the officer that there is an element of danger, but it wouldn't cause panic for someone who just overheard the transmission," Cannon said.

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Top 10 '10-codes'

10-4: OK

10-21: Call by telephone

10-22: Disregard

10-23: Arrived at scene

10-43: Information

10-46: Assist motorist

10-50: Accident

10-60: Squad car in vicinity

10-95: Prisoner subject in custody

10-99: Wanted/subject with warrant

SOURCE: Central Illinois law enforcement and emergency personnel

Other common Illinois 10-codes

10-1: Unable to copy

10-2: Signal good

10-6: Busy unless urgent

10-7: Out of service

10-8: In service

10-9: Repeat

10-10: Fight in progress

10-16: Domestic dispute

10-17: Complainant

10-19: Meet with

10-20: Location

10-24: Assignment completed

10-25: Meet in person

10-27: Drivers license info

10-28: Vehicle registration info

10-32: Subject with gun

10-37: Suspicious vehicle

10-38: Stopping vehicle

10-41: Beginning duty

10-42: Ending duty

10-44: Permission to leave for...

10-55: Intoxicated driver

10-56: Intoxocated person

10-57: Hit and run

10-59: Convoy or escort

10-61: Isolate self for message

10-69: Message received

10-70: Fire alarm

10-76: En route

10-79: Notify coroner

10-90: Residential or business alarm at

10-96: Mental subject

SOURCE: Wikipedia