The CQ 50 Series phones can accommodate distinctive ring tones to help distinguish between internal and external calls. They can also ring differently for calls to different ring groups, queues or inbound phone numbers.
To hear the various tones offered by the phone perform the following key sequences: Menu --> Settings --> Basic Settings --> Ring Tone
From this screen you can listen to your options. You can change the tone here but more than likely your phone is programmed by a template on the phone system. Your best option is to contact your CQ-certified partner and let them know which Ring Tone you would like to utilize.