I was working on a security panel today and the following is what happened.
On the speaker of the butt set just before the 1st ring a small buzz click was heard and then after the first ring a carrier tone is heard for about 1 second and then a pause and then the next ring. Nothing else is heard except for normal rings after that.
It is as if another modem or panel is on the line and connecting on the first ring but not answering the call.
Has anyone experienced anything like this and/or what the blazes is it or could it be????????? I ran out of time to investigate it further on site with voltages, current, etc. but it seems very strange. Any thoughts from the masses would be welcome.
I have been told that this is normal CID. My question, is it???