Self-calibrating seismic amplifier and telemetry system

Abstract

A frequency modulated, constant bandwidth, telemetry system has been designed to transmit simultaneously up to 8 channels of seismograph data from remote locations to a central recording site via radio or voice-grade telephone circuit. By utilizing state-of-the-art integrated circuits, the size of the remote unit has been considerably reduced over previous equipment and the power consumption has been decreased by a factor of over 100 to less than 2 milliwatts. This reduction in size and power makes it possible to package the electronic equipment, together with a year's supply of batteries, in a container the size of a tennis-ball can. The field equipment for a short-period station is now sealed in a 3-inch plastic tube 22 inches long . The tube, together with the connecting cable to the telephone terminal, is buried; greatly reducing losses due to water flooding, pilferage, etc. An important addition to the field unit is a daily calibration of the seismometer and amplifier. Specifications and instructions for the three units that compose the system are presented separately, as follows: 1. J302 Preamplifier and voltage controlled oscillator 2. C-4 Calibrator 3. J101 Discriminator