A 10 code is any one of the communication codes starting with 10, often used by both government and private institutions to provide a basic framework for communications in the facility. 10 codes are implemented by giving employees a Two-way Radio which they can use for communication between the control center and each other.
10 codes are not regulated and are often adapted by corporations to suit their needs and wants, however the most basic ones to tend to stay the same.
One of the main reasons a Urban Explorer would want to carry a list of 10 codes with them is to listen in to security, police, fire, EMS, maintenance, or general communication frequencies and gather information. A typical conversation may go as follows, with persons signified as letters:
A: 635 to 638. B: 638, go ahead. A: 10-34 south entrance ground, multiple 10-12. B: Roger, 10-6. B: 291, 10-200 south entrance ground level. C: 638, 10-4, notifying.
To an unprepared listener this may sound like gibberish, but to someone armed with the knowledge of 10 codes this can provide a wealth of useful information. Let's see what it would look like if this was spoken in plain English:
A: 635 to 638. B: 638, go ahead. A: Trouble at south entrance ground level, help needed, multiple visitors. B: Roger, please stand by. B: 291, police needed at south entrance ground level. C: 638, got that. Notifying cops.
In this situation the knowledge of the 10 codes may mean the difference between getting out of there and getting busted.
Here's a list of the most commonly used 10 codes. Please note that while these do vary company to company, a lot stay the same.
(EDIT 3/16/07): The above paragraph is NOT factually accurate. 10 codes vary widely from department to department, county to county, state to state. The below should NOT be used as a reference. Use the internet to search for the organization's 10 codes you are looking to decode.
10-1 Receiving Poorly 10-41 Please Tune To Channel 10-2 Receiving Well 10-42 Traffic Accident At___________ 10-3 Stop Transmitting 10-43 Traffic Tieup At______________ 10-4 OK, Message Received 10-44 I Have A Message For You 10-5 Relay Message 10-44 (Or__________________________) 10-6 Busy, Stand By 10-45 All Units Within Range Report 10-7 Out of Service, Leaving Air 10-50 Break Channel_________________ 10-8 In Service, Subject To Call 10-60 What Is Next Message Number? 10-9 Repeat Message 10-62 Unable To Copy, Use Landline 10-10 Trnsmssn Cmpltd, Stndng By 10-63 Net Directed To_______________ 10-11 Talking Too Rapidly 10-64 Net Clear 10-12 Visitors Present 10-65 Waitng for Nxt Msg or Assngmnt 10-13 Advise Wx and Road Conditions 10-67 All Units Comply 10-16 Make Pickup At_______________ 10-70 Fire At_______________________ 10-17 Urgent Business 10-71 Prcd With Trnsmssn In Sequence 10-18 Anything For Us? 10-73 Speed Trap At_________________ 10-19 Nothing For You, Rtrn To Base 10-75 You Are Causing Interference 10-20 My Location Is_______________ 10-77 Negative Contact 10-21 Call By Landline 10-81 Reserve Hotel Room For________ 10-22 Report In Person To__________ 10-82 Reserve Room For______________ 10-23 Stand By 10-84 My Telephone Number Is________ 10-24 Completed Last Assignment 10-85 My Address Is_________________ 10-25 Can You Contact______________ 10-89 Radio Repairman Needed At_____ 10-26 Disregard Last Information 10-90 I Have TVI 10-27 I Am Moving To Channel_______ 10-91 Talk Closer To Mike 10-28 Identify Your Station 10-92 Your Tx Is Out Of Adjustment 10-29 Time Is Up For Contact 10-93 Chck My Frqncy On Ths Chnnl 10-30 Does Not Conform To FCC Rules 10-94 Please Give Me A Long Count 10-32 I Will Give You A Radio Check 10-95 Tnx Dead Carrier For 5 Seconds 10-33 EMRGNCY TRFFC AT THIS STATION 10-99 Mssn Cmpltd, All Units Secure 10-34 Trbl At Ths Sttn, Help Needed 10-100 5-Min. Brk, Commonly RestRoom 10-35 Confidential Information 10-200 Police Needed At______________ 10-36 Correct Time Is______________ 10-37 Wrecker Needed At____________ 10-38 Ambulance Needed At__________ 10-39 Your Message Delivered
To keep the thread short I'll only post the link. I've found that many jurisdictions use different 10 Codes. Those found at this link are more applicable to police use: http://www.phreak.org/radio/tencode.html
Addendum: Many departments and organizations throughout the United States and Canada are ELIMINATING the use of 10 codes entirely. This is because as radio systems focus on interoperability (the ability for two or more dissimilar radio systems to communicate), it is not efficient for organizations to use 10 codes any longer as each organization uses different 10 codes. 10 codes will likely become a thing of the past, sooner rather than later.