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Inductance calibrations at PTB are carried out with a Maxwell-Wien bridge. This bridge has the advantage that the first order bridge equation is independent of frequency which means that the bridge has the potential to be operated in a large frequency range. However, the actual frequency range, from power frequencies up to 1 MHz, requires an investigation of higher order effects.

Development of the first US national fiber-optic transmission network, during a period marked by the rapid and technology-intensive introduction of single-mode cable and high-capacity optical transmission equipment is discussed. The authors examine some of the important design issues addressed during the development phase including baseband treatment, surveillance system homogeneity, capacity upgrade capability, network survivability, and flexibility for future growth. >

Two computer-controlled capacitance bridges for different fields of application have been developed at the PTB. The first one, the universal bridge, works in the capacitance range of less than 1 pF up to 1 /spl mu/F and in a frequency range up to 1 kHz, The total calculated relative uncertainties (2/spl sigma/) are in the order of 5/spl middot/10/sup -6/ and 20/spl middot/10/sup -6/. The second one, the fixed ratio bridge, calibrates primary standards with capacitance values from 1 pF to 1 nF in 1:1, 1:2, 1:5 or 1:10 steps at frequencies from 100 Hz to 10 kHz. The relative uncertainty of one 1:10 step at a frequency of 1592 Hz is estimated to be 3/spl middot/10/sup -8/ (1/spl sigma/). >

An intercomparison of standard capacitor of value 10 pF has been carried out between NPL (India) and Physikalisch-Technische Bundesanstalt (Germany) under the PTB-NPL Cooperation programme. The measurements of a 10 pF silica capacitor at the frequency 1592 Hz for two different temperatures agreed within 0.15 ppm.

Aiming to relating the Farad to the Ohm, reproduced at Centro Nacional de Metrologia (CENAM) by means of the Quantized Hall Effect (QHE), a development project was planed. The results of the construction of a capacitance bridge that constitutes the first step to achieve this objective are presented.