Do the analog Starplus systems not provide disconnect supervision? If I have a call on hold and the caller hangs up, the line remains on hold.

The STS has supervision. I ran into trouble the other day when one line wouldn't drop but others would. I found Telco wasn't sending me enough of a polarity reversal. The voltage would drop to about half a volt but not go all the way to 0 volts. The duration was OK about .5 seconds. I explained it to the Verizon Tech, he had never heard of it before but he fixed it and it works fine now.

The analog Starplus probably does not have DS. That's just one of the many reasons why VM doesn't work good on those analog systems.

You are correct, the old analog KSU's did not have supervision.

Kind of annoying to get back to a caller and find taht they're not there....o well, nothing I can do about it.