Not only the bargain offers in the bay, but also as a backup system for the hp58503B (GPS disciplined OCXO) made it necessary to have such a nice thing.

As there is almost everything done, we may use the space and time (saved) to build an interface with some additional features. An Atmega 8 reads some analog voltages like supply or lamp voltage and feeds an lcd with the data. The words "locked", printed on a screen or display are more informative than just a led, which when not lit mayst be defective. Beyond that, it is the occasion to learn this ADC stuff, sleeping (up to now) in the Atmega :-)

The circuit is straightforward. The power supply has been designed out of the case. This allows for battery powering, when necessary. As the power consumption of the Atmega 8 and the lcd is low, a linear regulator generates the +5V out of the +24V. Regarding the output of the LPRO-101, it has series resistors of two times 10kΩ inside, so we added a shunt of 4kΩ. This guarantees, that the analogue inputs of the Atmega stay below 2.5V. None of those measurements are time critical, so running at 1 MHz is absolutely sufficient. The circuit was realised on a double sided pcb. In case the serial comunication is used, the crystal may be adapted, depending on the datarate.