Zitat aus Joint Laser Designation Procedures (Joint Pub 3-09.1)   
Designator and Seeker Pulse Codes. The designator and seeker 
pulse codes use a truncated decimal system that uses the numerical 
digits 1 through 8, and the codes are directly correlated to a 
specific PRF. Depending on the laser equipment, either a three- or 
four-digit code can be set. Three-digit code equipment settings 
range from 111 to 788. Four-digit code equipment settings range from 
1111 to 1788. The three-and four-digit code equipment is 
compatible, and any mix of equipment can be used in all types of 
laser operations. However, when using a mix of three- and 
four-digit code equipment, all personnel must understand that the 
first digit of a four-digit code is always set to numerical digit l. 
The remaining three digits will be set to match the three digits of 
the three-digit code equipment. As an example, a three-digit code 
of 657 would be set to 1657 on a four-digit code system or vice 
versa.