SILENCE
Indicates the maximum number of entries a user may have in their silence list. The value is OPTIONAL and if not specified indicates that there is no limit.
The "SILENCE" command seems to vary quite a lot between implementations. Most clients include client-side filter/ignore commands and servers have the "CALLERID" client mode as alternatives to this command.
Format: SILENCE=\[number]
Examples:
SILENCESILENCE=15