Updated 25-VIII-2003
Mercury Vapour
Mercury Pressure
Mercury Spectrum
Lamp Nomenclature
Timeline of Developments
Mercury Vapour
J.T. Way
Küch and Retschinsky
MA Medium Pressure
The first lamp
The first installation
Lamp developments
Striking the discharge
Operating characteristics
Glass technology
Electrode technology
Production methods
MB High Pressure
MC Low Pressure
MD Water-Cooled
ME Super Pressure
UHP Ultra High Pressure
Mercury Vapour
Fluorescent Coated Lamps
Tungsten Ballasted Lamps
Lamp Electrodes
Additives to the Arc
Electrodeless Designs
Future Developments
Mercury Vapour
High Pressure Circuits
Low Pressure Circuits
Electronic Operation

MA Medium Pressure Lamps

Until 1932 illumination with mercury lighting had been a complicated affair with unreliable lamps that required horrendously complex control systems.  They were a true nightmare to manufacture, and they also gave a poor quality of light with only a moderately good system efficiency.  As a result they were confined exclusively to areas which either needed a very large amount of light and the colour quality was of no concern (i.e. in photo-printing shops), or for use as ultra-violet sources in special laboratory and medical applications. 

That all changed in June 1932 when the Osram division of the General Electric Company of England unveiled its new "Osira" lamp which was to revolutionise the future of electric discharge lighting worldwide.  It was the first time that a discharge lamp had been offered in a compact, clean and efficient package which customers could instantly appreciate how to use in new applications with the utmost simplicity.  A 1933 advertisement for the new lamp is reproduced in Figure 18 to the right.

So many of the features on which virtually all modern discharge lamps rely were introduced at this time, indeed it would not be inaccurate to describe this British development as the first practical discharge lamp on which nearly all modern descendents are based in one way or another.  It introduced many 'firsts', for instance:

  • An arc tube sealed within in a transparent outer bulb for thermal insulation

  • A simple single-ended design with screw cap for ease of installation

  • An unsaturated vapour in which the entire mercury dose is vaporised

  • A compact arc to facilitate its use in ordinary optical systems

  • A hot cathode to enable high power loadings

  • A simple starting system which relies on no moving parts

  • Operation from a simple choke-type ballast

On the following pages in this section, full details pertaining to the first lamp and the first installation of mercury streetlighting can be found, and the complete development of the MA Medium Pressure Mercury lamp is followed right up to the time at which it was eventually superseded by higher pressure MB versions.