Both ideas have merit.
I appreciate the info from MORA regarding opto couplers… I was familiar with solid state relays, but opto couplers seem to be more in line with my application. I’ve been researching them online. Apparently I’m looking for an AC optocoupler. Most of the ones I’ve found are similar to relays… a small signal is used to switch a larger signal. My application is a bit different since I’m switching a small dc voltage with a relatively high AC voltage. I’m confident that with some research I could find one ideally suited for my application. This option’s advantages include relatively low cost, and more immunity to RF interference than the competing option. The disadvantage is it requires a physical connection to the circuit.
I’ve also been looking at CTs’. My concerns with the CT are relatively high cost, possible vulnerability to rf interference (relatively high power vhf radio transmitters are nearby). The advantage, of course, is no physical connection is required.
Expanding the idea of “isolation” a bit further… keeping in mind that this option would cost more… I’m wondering if any type of wireless solution is available… clip something on to a wire that signals its on/off state to its mate… Brainstorming… perhaps others have some ideas.
On a side note… I appreciate that the community is responding and contributing to my inquiry… Thanks folks!