In one aspect, a phone-interface device determines whether a problem has occurred at a control panel by determining whether a signal from the control panel has been received, and when a signal has not been received within a period of time, the phone-interface device transmits an error message to a monitoring station. In another aspect, the control panel determines whether a problem has occurred at the phone-interface device by determining whether a signal from the phone-interface device has been received, and when a signal has not been received within a period of time, the control panel transmits an error message to a user. In another aspect, the phone-interface device contains memory to buffer data transferred between the control panel and a monitoring station. In this way, a high-speed connection between the phone-interface and the monitoring station can be accommodated while using a lower-speed connection between the phone-interface device and the control panel.