Before revision: Instrument and sensor manufacturers Four companies supply most of the commercial-use world market: one in the United States (Zonge International, Inc.), one in Canada; (Phoenix Geophysics, Ltd.) , and one in Germany (Metronix Messgeraete und Elektronik GmbH).)
After revision: Instrument and sensor manufacturers Four companies supply most of the commercial-use world market: one in the United States (Zonge International, Inc.), one in Canada; (Phoenix Geophysics, Ltd.) ; one in Germany (Metronix Messgeraete und Elektronik GmbH).)