[time-nuts] Trimble Thunderbolt- Frequency lock indicator

[Wojciech Tomczyk]

I use an early Thunderbolt as a 10 MHz external frequency standard for my Elecraft K3 transceiver.I would like do add to it a simple indicator which is activated when Thunderbolt's output frequency is locked.I someone aware of a circut diagram of a such indicator? Any other options to indicated the LOCK state?
Tom