What is a selcal code?
The selcal code is the what makes the paging system function. A selcal code is made up of two 2-letter pairs between the letters A to S in the alphabet (the letters I, N and O are not used). The first letter of each pair must be earlier in the alphabet that the second letter and duplicate letters are not permitted (although there are a very small number of exceptions) thus giving a total of 10,920 unique codes.