); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I'm working on a synth. project which can take either an external 10MHz reference input or use an internal TCXO. It would be nice if the presence (or more importantly, failure) of the external 10MHz ref. could be detected automatically, and signaled to the user.
There are, of course, a number of ways to do this. One is to use a level detecting circuit; simply AM detect the ext. ref. input and apply to a comparator. Lots of circuits to do this, no problem - but requires a number of components, unless there is some magic IC that will do it that I'm not aware of - I suppose a dual op-amp is all that's needed, plus a handful of discretes. Another option might be to use a re-triggerable monostable, which is constantly looking for the presence of (say) a falling edge every 100nS on the ext. ref. input line. It would seem that conceptually, this would be the easiest way, possibly using less components. Does anybody have any favourite circuits for this; or are there any caveats that are not mentioned in the plethora of monostable circuits that are mentioned on the 'web? Mnay (older) test equipments have an int/ext switch on the back, with an indicator on the front, but some newer ones detect the ext. ref. and switch automatically. I suppose that's not a problem on a $$$$ box, which this synth. is not. The output would simply be a high/low digital line, the ext. ref. input will of course be buffered; I can cope with switching the 10MHz signals. Any ideas appreciated. regards Grant _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
