3 what is this tone, 1 what is this tone, While on-hook when going off-hook – Panasonic HYBRID IP-PBX KX-TDA30 User Manual

3 what is this tone, 1 what is this tone, While on-hook when going off-hook | Panasonic HYBRID IP-PBX KX-TDA30 User Manual | Page 218 / 232