RJ21: 50 Pin connector
RJ45: keyed 8P8C
8P8C: This is what is know "called" RJ45, and it has no key
RJ48: 8P8C
RJ50: 10P10C
RJ9: 4P4C, used for Telephone Handset cables.
RJ10, RJ22: 4P4C, used for Telephone Handset cables.
RJ11: 6P4C, ADSL Telephone and Modem.
RJ12: 6P6C, System Phones.
RJ14:
RJ25: 6P6C