+ mISDNSIGNAL_VOLUME, /* change volume */
+ mISDNSIGNAL_CONF, /* joint/split conference */
+ mISDNSIGNAL_CALLDATA, /* data required by call instance */
+ mISDNSIGNAL_ECHO, /* enable/disable echoe */
+ mISDNSIGNAL_DELAY, /* use delay or adaptive jitter */