I have an SLT connected to Port 8, when accessed I get broken dialtone-Tone silence for 1.5 sec 2 tones, silence for 1.5 sec.I can't break dialtone at all-no outdialling or internal dialling. I've hit the reset button and have executed a hard shutdown to no avail. Can't find anything relevant in the install guide or User Guide. No extra ports on system.