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The company now known as a semiconductor giant and maker of hand-held calculators started out as Houston Technical Laboratories, the instrument manufacturing subsidiary of Geophysical Service, Inc., one of the leading geophysical contractors from its formation in 1930 until the mid 1980's. From the late 1950's until 1981 TI was a major supplier of seismic recording systems to the industry.
Early GSI recording systems were probably not formally named, but by the mid 1950's each model was a number ending in 000. The 7000 system was introduced in about 1956, and was advertised as the Standard Seismic Recording Instrument for the International Geophysical Year (1956-57). This was an all vacuum-tube system, running from a bank of 12 volt batteries in the recording truck. Its standard recording medium was the MagneDisk, a predecessor of the floppy disk used on today's computers, and quite a technical accomplishment for the time. Many 7000 systems used magnetic recorders built by other instrument companies such as Techno, and some used no magnetic recorder at all, relying on the photographic recording made by field systems since the earliest days of seismic exploration.
The next model introduced was the 8000, and used transistors throughout. It was much more portable than earlier systems, but did not compete very well with the SIE PT-100. This system was widely used by GSI field crews until the early 60's.
Meanwhile, GSI had started work on a designing a digital seismic recording system, jointly with Esso (now Exxon). The first practical system (using the term "practical" in a loose sense) was the combination of the Digital Field System (DFS) with the new Series 9000 Seismic Amplifier, which was advertised in December 1964 as having over 440 crew-months of field experience. The same month the annual Geophysical Activity Report showed nearly 8200 crew-months of seismic field operations in the "Free World" in 1963, the DFS experience spread over at least two years (a 1971 advertisement gives the date of the DFS 9000 as 1961) is not very large. But these were the first real digital recording systems, even if they had reverted to vacuum tubes, and had no Automatic Gain Control (AGC).
A year later, GSI was advertising the DFS-10000. This was a transistorized system, but still not exactly portable. Though not a fixed gain system (it used "ganged AGC"), the 10000 claimed only 78 dB dynamic range, a substantial improvement on the 50 dB or so dynamic resolution of the analog systems of the day, but not as good as the analog systems when they used automatic gain control on individual channels. Still, the digital system could make absolute measurements of the recorded signal, a feat which was almost impossible with the analog systems.
By June 1967 Texas Instruments had started to offer the DFS-10000 to customers other than GSI. This advertising continued until December of that year.
In February 1968 Texas Instruments started to advertise the DFS III. If the original DFS with 9000 amplifiers was the first generation Digital Field System, and the DFS-10000 was the second generation Digital Field System, then the new system was the third generation Digital Field System or DFS III.
This system was reasonably portable, only 370 lb. (168 kg) and 440 W power consumption for a 24 channel system. In place of fixed gain, it had binary gain, with the recording gain of each channel being switched in 2:1 steps to bring the geophone signal within the range of the 15 bit analog to digital converter. A dynamic range of 174 dB was optimistically claimed, with dynamic resolution of 84 dB.
The DFS III proved to be a very robust and reliable system. It was the first TI seismic system to use integrated analog and digital circuits ("chips") on a large scale, and was still in widespread use 10 years later.
The DFS IV was announced in late 1970, with the big innovation of instantaneous floating point gain: the gain was changed for each sample so that the amplitude of the signal input to the converter was nearly at full scale. The system claimed to be easier to maintain than the DFS III, and was easier to expand to large numbers of channels, but it proved to be less robust than the DFS III, and had few operational advantages. It was widely used for marine recording, but most land crews held on to their DFS III's for a few more years.
In August 1975 Texas Instruments started advertising the DFS V. It was a dramatically more compact and lower power system, offering up to 120 channels in only four "man portable" modules. A 48 channel system used about half the power and weighed half as much as a 24 channel DFS III or DFS IV. The performance in terms of dynamic resolution and dynamic range was comparable with the DFS IV, but the system proved to be far more reliable and easy to maintain. By the time the seismic industry collapsed at the end of 1981, TI had delivered over 1000 systems, which will probably remain an all time record for number manufactured of any one design of seismic recording system.
The DFS V owed its high performance to the use of very large scale integrated CMOS chips. Its chief designer was Paul Carrol, who later moved to Input-Output
In about 1980, Texas Instruments started showing large customers specifications for the DFS VI. It was not to be a digital telemetry system, but allowed more recording channels than the DFS V with shorter sample intervals. Advertisements for the DFS VI first appeared in December 1980, and continued for about a year. I have not heard of a single system being sold.
Advertising for the DFS V reappeared in about March 1981, and continued in various forms until late 1983.
In December 1983 Texas Instruments advertised the DS100, a digital telemetry system which fed data to a DFS V Controller and tape system. I do not know if a full system was ever built, and Texas Instruments quietly faded from the scene as a supplier of geophysical recording systems shortly afterwards.
The Input/Output System One was introduced at the 1987 SEG meeting.
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