Communications: electrical – Selective – Having electron beam device
Patent
1975-08-27
1976-10-19
Moskowitz, Nelson
Communications: electrical
Selective
Having electron beam device
325 30, 325 45, 346 33C, G01V 122, H04B 714
Patent
active
039874060
ABSTRACT:
In seismic group recording, each seismic trace is initially digitally recorded by a small, portable, magnetic recorder placed near the corresponding seismometer recorder group. A large number of such groups and corresponding recorders are placed over an area or along a profile line, and from a control point, only those specific recorders needed for a given set of record traces are turned on at any time by transmitting a set of coded signals over a communications link which is usually a radio link. The bandwidth restrictions of licensed geophysical radio channels can cause difficulty in this communications system from control point to the various seismometer groups. Accordingly, this disclosure covers an improvement in the communication method employed in a seismic group recorder system. U.S. Pat. No. 3,806,864 teaches the employment of audio frequency encoding on a frequency-modulated band-limited channel with a maximum audio frequency of approximately 3 kilohertz. As initially used, on-off keying of three different tones was employed, due to simplicity. The present system is an improvement employing coherent frequency-shift keying, in which several different audio frequencies, bearing certain relations to each other, are employed. This results in near optimum communication for control of the seismic group recorder system over a voice-grade standard, geophysical licensed radio link.
REFERENCES:
patent: 2700753 (1955-01-01), Peterson
patent: 3764913 (1973-10-01), Ochel et al.
patent: 3773975 (1973-11-01), Koziol
patent: 3794928 (1974-02-01), Stump et al.
patent: 3806864 (1974-04-01), Broding et al.
patent: 3838342 (1974-09-01), Bjorkman
patent: 3886494 (1975-05-01), Kostelniak et al.
patent: 3916371 (1975-10-01), Broding
Moskowitz Nelson
Pottorf Newell
Standard Oil Company (Indiana)
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