In Metal Gear Solid 2: Sons of Liberty, players will once again be able to call upon various allies for advice using the Codec. A staple of the Metal Gear Solid series, the Codec allows Snake and Raiden to communicate silently with any number of allies by utilizing nanomachines. Players will need to know a character's Codec frequency in order to actually contact them, though luckily, the game saves all Codec frequencies that have been used at least once to prevent this from becoming frustrating.