Simple Telemetering System for Signaling High Rumen Pressures

The construction of a modified Hartley oscillator transmitter activated through a pressure switch is described. When this device is placed within the rumen of a cow which is allowed unrestricted movement in the pasture, frequency-modulation signals are transmitted to a recording receiver whenever a preselected pressure is exceeded. The pressure at which transmission begins is determined by the capacitance across the coil of the circuit.