Not sure why you would want to do this but, if you have a Rb, such as an LPRO-101 or others, there is a signal that lets you know the Rb is 'locked'. You could use that to drive a relay that would switch the output of the Rb to the external input of your device.
This presumes you do not have to mechanically flip a switch on the device to select internal or external references. On an OCXO, I guess you could sense the oven current and, when it goes low, indicating that the oven is 'warm', that could be used to drive the relay to send the output of the OCXO to the device. Otherwise, you would need a 'house standard', that is always on, and measure how far apart the OCXO is from your 'house standard' and switch when your OCXO meets certain performance specs. In that case, why not use the 'house standard' all the time? Might be easier to build a battery back-up for your 'house standard'. Hope this helps. Joe -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Joseph Gray Sent: Sunday, December 09, 2012 3:13 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Switching oscillators I have a device that has an internal TCXO. I want to feed it with an external OCXO, but I don't want to completely replace the TCXO. Here is the scenario. On initial power on, or after a power loss, I want the internal TCXO to be used. Once the OCXO is up, I want to switch to it. How could this be done easily and cheaply? Joe Gray W5JG _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.