The 13 Volt input connects (through a diode) to the DC rail in the
Power Supply, upstream from all the regulators, downstream from the
full wave bridge. It is always connected.

The regulators would draw power from both the AC/transformer/bridge
and from the battery/diode if both were hooked up.

On Wed, 26 Nov 2003 21:06:54 GMT, "Peter"
wrote:

I have a question about this radio.
If I plug the AC jack in the wall and I have the 12 volt connection hooked
up to a battery as a power failure backup will it damage the radio? Is there
an internal switch to protect it from both sources being connected at the
same time?

Thanks

Pierre