The call sign for a translator starts with the same letter as the call sign of the primary station. This letter is followed by a three-digit number indicating the FM channel of the station. This number is followed by two letters which indicate the order in which the translators are licensed. For example, the first translator on the east coast that operates at 88.1 MHz is given the call, "W201AA", the second is given the call, "W201AB", the third is "W201AC", and so on.
Translators are similar to FM booster stations except that translators operate on a different frequency than the primary station, while boosters operate on the same frequency.
For more information on FM Translators and Boosters, please see the FCC's Website.