I have a DSC Power Series 632 system with a 1555mx main board. The system is monitored and TLM is enabled. I am getting a Trouble Code #3 whenever my phone line goes off hook. The trouble disappears when the phone goes back on hook. The monitor company is getting messages all day long about phone line being restored. I check the incoming voltage for T&R on the panel. I have 50v dc when the phone is on hook and about6.5v dc when the phone is off hook. The system communicates just fine with the monitoring company. I am only having problems when I am trying to use my shared phone line.