Yes, it is possible to choose different ring tones for internal and external calls. How to set up differs depending on whether you have an analog or SIP based system. If a SIP based KIRK Wireless Server Solution is used, the internal/external signal may depend on a specific SIP Header. On the analog based KIRK Wireless Server Solutions the ringing frequency may need to be adjusted to follow the ringing cadence from the PABX. Please contact your local distributor or installer for assistance.