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FXO Port Hang up

For FXS port, we already know that there is a "glare" problem we maybe meet. For FXS ports, we regularlly met the situation of FXO port hang up. It confused me for a long time. Is there anyone kindly explain the detail princicples of the cause of "fox port hangup" . Any advice will be appreciated.

Robert Li,ming


Re: FXO Port Hang up

When loop-start signaling is used, a router's FXO interface looks like a phone to the switch (private branch exchange (PBX), public switched telephone network (PSTN), Key-System) it connects to. The FXO interface closes the loop to indicate off-hook. The switch always provides a battery so there is no disconnect supervision from the switch side. Since a switch expects a phone user (example of an FXO interface) to hang up the phone when the call is terminated (on either side), it also expects the FXO port on the router to hang-up. This "human intervention" is not built into the router. The FXO port expects the switch to tell it when to hang-up (or remove the battery to indicate on-hook). Because of this, there is no guarantee that a near-end or far-end FXO port disconnects the call once either end of the call hangs-up.

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