Since 1987 the Quantum Magnetometry Laboratory (USTU, Ekaterinburg, Russia) produces the magnetometers POS-1 using the processor Overhauser sensor technology (POS - Processor Overhauser Sensor). Magnetometers are used for geology survey, magnetic observatories, seismic and volcanic monitoring, and as first reference standards of weak magnetic field induction. POS-1 were installed for continuous recording at a number of Geophysical observatories. Three-year results of using POS-1 in observatory practice are presented in this report. The installation requirements, the used hardware and software and particularities of the operation are described. POS-1 is used as an absolute device for determination of variometer baselines and as a device for independent control of variometer data. POS-1 has shown itself as an effective tool for the investigation of the magnetic field spatial distribution at observatory area and in magnetic huts.