The amplifier has a similar topology to the Williamson amplifier published in Wireless World in 1947.In 1948, the original four-stage circuit was replaced with a three-stage design that was designated the TL/12.

helium leakage dating-20

This represented a major leap forward in accepted standards for high-performance amplifiers (with 2% distortion generally considered acceptable at the time).

This first "Point One" amplifier was known as the Type 15, and produced 15 watts output, at 0.1% distortion, using push-pull KT66 valves connected as triodes, with 26 d B feedback applied over four stages.

The company was founded in 1934 by Harold Joseph Leak and was sold to the Rank Organisation in January 1969.

The company initially focussed on provision of amplifiers for public address systems and theatres, with only a few staff.

CFCs have been increasingly used in oceanic studies since the late 1970s as tracers of oceanic circulation, ventilation, and mixing processes.

USGS scientists (Busenberg and Plummer, 1992) adapted analytical procedures developed by the oceanographic scientific community for ground-water studies and designed sampling equipment and procedures for collection and preservation of water samples in the field.Chemical processes, such as microbial degradation and sorption during transit, can also affect the concentration of CFCs and other compounds used in dating.For this reason, the term “age” is normally qualified with the word “model” or “apparent,” that is, “model age” or “apparent age.” USGS scientists have investigated some of the most important factors that can affect CFC concentrations in ground water and the resulting age interpretations (Busenberg and Plummer, 1992; Plummer and others, 1993; Dunkle and others, 1993; Ekwurzel and others, 1994; Cook and others, 1995; Plummer and others 1998a, 1998b; Plummer and Busenberg, 1999).This approach had been patented by Harold Black of Bell Telephone Laboratories in 1934, and already used before that by Alan Blumlein of EMI, but it was slow to emerge as popular method for controlling amplifier performance.In September 1945 the company released the first of the "Point One" series of amplifiers, so named because the total harmonic distortion was 0.1% at rated output.Water samples for CFC analysis are now routinely collected from domestic, irrigation, monitoring, and municipal wells, and from springs. Nuclear Regulatory Commission-licensed USGS laboratory for analysis of CFC content by gas chromatography to a detection limit of about 0.3 picograms per kilogram (0.3 pg/kg) of water, which is equivalent to 0.3x10 Ground-water dating with CFC-11, CFC-12 and CFC-113 is possible because (1) their amounts in the atmosphere over the past 50 years have been reconstructed, (2) their solubilities in water are known, and (3) concentrations in air and young water are high enough that they can be measured.