The Complete Book of Dwarves[]
Sign language is most frequently used by dwarves who were engaged in long running warfare with other dwarves or races. It permits silent communication with anyone who sees and understands the signals. The maximum range is usually line of sight in a lit area, or the extent of the receiver's infravision. Sign may be an extensive language capable of handling long conversations, or simply a means of communicating a few easy to understand phrases such as "attack," "orcs behind the rock," or "you three move left." A proficiency check is made when speaking or interpreting sign. The +2 bonus should only be used when giving short, easily recognized commands. More detailed signals require a -1 modifier.
The Complete Barbarian's Handbook[]
A character with this proficiency can communicate with hand movements instead of speech. Sign language can convey messages of the same complexity and nuance as a spoken language, providing the participants can see each other's hands.
If two characters with this proficiency wish to communicate, both must make proficiency checks. If both succeed, they may use sign language to silently converse for a full round. They may continue their conversation by making successful checks on subsequent rounds. During a round when either character fails his check, the communication is garbled; the sender's finger movements weren‘t precise, the receiver wasn't paying attention, or something blocked the line of sight. On a natural roll of 20, the receiver interprets the message as the opposite of what the sender intended.
A character with this proficiency may also try to convey a simple message to a character without the proficiency. The player must first whisper the phrase to the DM, who decides if the phrase is acceptable. Acceptable phrases include “Don't move,” “Follow me,” and ”I'm hurt.” Complicated phrases or those containing proper nouns are unacceptable, such as ”My name is Grog,” 'Take three steps north, then look up,” and ”We can find the antidote in Elk Valley.” If the DM deems the phrase unacceptable, sign language can't be attempted; no proficiency check is necessary. If the DM allows the phrase, he character makes a check.
If the check succeeds, the phrase is successfully communicated. If the check fails, the phrase is garbled. On a natural roll of 20, the receiver misunderstands the phrase, interpreting it as the opposite of its actual meaning. A character can't attempt to communicate the same phrase more than once to the same recipient.
Crossover Group:: General
Dark Sun Campaign Setting Revised[]
Those who have mastered the use of sign language can communicate among themselves without words, provided they can see each other's hands. Signing is a language unto itself: It conveys ideas that any other character who has the sign language proficiency can understand, regardless of his or her native language.
To use sign language for an entire round, all parties involved must make a successful check. Characters who succeed can converse together for an entire minute; those who fail can't listen. When a PC signs successfully with an NPC, the DM should speak freely with the player for one minute per round. Every round of conversation requires another check. A failed check means that the speaker didn't perform his finger movements accurately, the listener wasn't watching the speaker closely enough, or something else blocked communication.
On Athas, many groups employ sign language for covert conversations. In some citystates, using sign language can be grounds for imprisonment. Though sign language throughout Athas is generally consistent, some secret societies employ special codes so that unwanted eyes can't decipher specific conversations.