The directed bright-field (see Fig. 1) has extremely strong directional characteristics by means of a point source and an optical system (condenser); in this case, each point of the photographic film receives light from only one direction.
A 28 inch cylinder inverted engine designed by Edward Bull, chief designer for Boulton and Watt, was put into Ding Dong in 1796; James Watt saw this as an infringement of his 'condenser patent'.
Electret materials have been known since the 1920s and were proposed as condenser microphone elements several times, but they were considered impractical until the foil electret type was invented at Bell Laboratories in 1962 by Gerhard Sessler and James West, using a thin metallized Teflon foil.
He invented the spiral cold finger-type condenser, now most commonly known as a Friedrichs condenser, which he described in a 1912 article published in the Journal of the American Chemical Society.
In the United States, for example, the "sound" of the best-known crooners of the 1940s (e.g. Bing Crosby and later Elvis Presley) had utilized the ultra-smooth, rolled-off tone of RCA ribbon microphones; pop recordings in the 1950s (e.g. Frank Sinatra and later The Beatles) on the other hand were sharper, clearer, much more "present" and more "hi-fi"-sounding as the result of using condenser microphones with elevated upper-mid-range response.
These studies include Bhabha Atomic Research Centre Pre-operational Baseline Radiological Survey of the Area around JNPP Site, Central Water and Power Research Station Pune, Thermal Dispersion Studies for Condenser Cooling Water (CCW) Discharges, Konkan Krishi Vidyapith, College of Forestry, Dapoli, Baseline Biodiversity Study of the area around JNPP Site.