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.

sounds like hotline/pickup dial may be set to some random string.

if you get a second of dial tone try picking up the phone and dial 790 as quick as you can, if not you will have to change hotline/pick up dial timer to give you time to do it

Can you call that extension

Yes, you can call it. I did try the feature clear option 790 to no avail. I'll look up the hotline/pickup feature-thanks!

This is asuming you have a 2500 set available take the handset and cradle it on your shoulder put your left index finger on the hook button now lift your your leftindex finger an as fast as you can dial 740 with your right index finger if you get a confirmation tone hang up ,now go off hook do you get normal intercom dialtone?