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FXS port polarity

What's the difference between forward and reverse mode in FXS port polarity configuration for: Idle Polarity, Caller Conn Polarity and Callee Conn Polarity.

Can I keep line1 in forward mode and line2 in reverse mode

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Community Member

Re: FXS port polarity

The end-to-end connection between the CO RJ11 jack and the router voice-port must be a straight-through connection. This means that TIP goes to TIP and RING to RING. Normally the CO provides an interface for which a standard rolled RJ11 cable can be used since the connection that results is straight. However, sometimes the CO cannot reverse the pinouts and therefore, a straight RJ11 cable is needed.

Pinouts for Rolled RJ11 Cable => TIP to RING, RING to TIP

Pinouts for Straight RJ11 Cable=> TIP to TIP, RING to RING

Note: FXS ground-start services are polarity-sensitive and undesirable behavior, such as failed calls, can occur if proper polarity conventions are not observed.

http://www.cisco.com/en/US/tech/tk652/tk653/technologies_tech_note09186a0080094fac.shtml

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