The МХО37 series utilizes the internal heating resonator (IHR) technology incorporating the whole oven system together with the crystal plate inside the TO-8 vacuum holder. Such OCXO concept results in radical reduction of its volume, power consumption and warm-up time. The novel MXO37/8P version differs from the basic MXO37/8 model by improved oscillator circuitry providing essentially better temperature stability at the same miniature sizes, extremely low power consumption and low phase-noise level.