When a Type I system is designed, the address infor- mation for all its user IDs is divided into 8 equal-size blocks, numbered 0–7, and each block is assigned a size code. When you set up your scanner to track a Type I system, you must choose a size code for each block. When you have chosen a size code for all 8 blocks, you will have duplicated the fleet map for the system you are tracking. If you have chosen correctly, you will be able to track transmissions in that system.
Each size code defines the number of fleets, subfleets, and IDs each block has. For example, you can see in the following table that a size code of S-4 has one fleet, which is divided into 16 separate subfleets, and it has a total of 512 individual IDs.
Size | Fleets | Subfleets | IDs | Blocks |
| | | | Used |
| | | | |
| | |
S-0 | Reserved block for Type II IDs | |
| | | | |
S-1 | 128 | 4 | 16 | 1 |
| | | | |
S-2 | 16 | 8 | 64 | 1 |
| | | | |
S-3 | 8 | 8 | 128 | 1 |
| | | | |
S-4 | 1 | 16 | 512 | 1 |
| | | | |
S-5 | 64 | 4 | 32 | 1 |
| | | | |
S-6 | 32 | 8 | 32 | 1 |
| | | | |
S-7 | 32 | 4 | 64 | 1 |
| | | | |
S-8 | 16 | 4 | 128 | 1 |
| | | | |
S-9 | 8 | 4 | 256 | 1 |
| | | | |
S-10 | 4 | 8 | 256 | 1 |
| | | | |
S-11 | 2 | 16 | 256 | 1 |
| | | | |
S-12 | 1 | 16 | 1024 | 2 |
| | | | |
S-13 | 1 | 16 | 2048 | 4 |
| | | | |
S-14 | 1 | 16 | 4096 | 8 |
| | | | |
Each ID in the block is unique. The left-most digit is the block number in the ID. The next two digits identify which fleet is active, and the last digit(s) (after the hy- phen) identifies the subfleet.
