I've connected an IP security camera that has SIP phone capabilities to our CM 5.1. All the phones are Cisco SCCP phones. The camera is fully registered and can call any extension in our calling space. However when I try to call the camera from the phones, I get a fast busy. I'm not sure if it's a CM config issue or I missed something on the camera. What am I missing to get the SCCP phones to call SIP devices?