View Full Version : How to handle Loop Current Disconnect detection

10-29-09, 04:08 PM
Loop Current Disconnect detection:

When the far end hangs up the Telco will send the local side loop current disconnect signal. The Telco disconnects the line for a period of time (about 300ms) and then reconnects the line.

In our AoB product line we would determine this in the driver and then issue a LC_TERM event to the user application.

With AoH there is no LC_TERM event. AoH has the PKH_TRUNK_SetThreshold function which sets it for audio logging or normal modes. In normal mode the threshold is at - 4 volts. During a phone call if the voltage goes to zero volts, you will receive a PKH_EVENT_TRUNK_BELOW_THRESHOLD event. When it goes to talk voltage (- 8 volts), you will receive a PKH_EVENT_TRUNK_ABOVE_THRESHOLD event.

The users application will need to set a timer when you receive the PKH_EVENT_TRUNK_BELOW_THRESHOLD event. You want to see how long it is before you get the PKH_EVENT_TRUNK_ABOVE_THRESHOLD event, the length of time will determine if it was a disconnect signal from the Telco.

NOTE - Above the threshold means further from a zero value.

See the following function and events: