Open Source - Why doesn't Acknowledge call work with analog lines?

If an extension is on a Switchvox PBX and uses analog lines to connect the PSTN and calls are routed using a Ring All call rule to route calls to an external number and other extensions on the pbx, no extensions they add to the rule will ring.  When a call is sent to an analog channel, the analog channel immediately answers the call and sends it out to the PSTN. This occurs even though the person at the far end did not acknowledge the call yet.