Thanks for the explanation, Meindert. You've allayed my suspicions 1/2 way.
Padeen

"Meindert Sprang" wrote in message
...
"padeen" wrote in message
...
That's $250 US for a box with some connectors all wirenutted together
inside. "Optically isolated" means you can't see the wirenuts! There
must
be a less expensive way...

Well, an expander is bit more complicated than just a 'junction box'. It
contains an opto-coupler wich takes care of the optical- or galvanical
isolation. Next, there are a few buffers to give each output enough power
to
drive the required four listeners per output. And then the power supply,
this might vary from a simple three-terminal regulator to a more expensice
DC/DC converter (also isolated). Put this on a PCB, stuff it in a box, add
the usual markups and there you are at a pricelevel of around $150. So
indeed, $250 is a bit over the top.

Meindert