GEC BARRETTER, 1930's

Barretters are temperature sensitive resistors used for stabilising voltages in wireless receivers, usually powering the heater circuits, of AC/DC receivers.
Acting like a resistor but with constant current characteristics, a current over a particular range can be held constant over a range of varying voltage. A Barretter usually consists of an Iron wire held in Hydrogen filled glass envelope. Also used for many other applications.

Your comments:

• These were still used in the early 60s to give a constant current supply in a Hilger and Watts infrared spectrometer. The electronics unit contained 25 valves and the console stood 1.5m high.
  
  .......... Alan Roden, Harlow, 13th of May 2019
  
  
• Back in the early 1950's While working for Tung-Sol Electric Bloomfield NJ. we made Smaller units in 9 Pin Miniature tubes called Ballast Lamps for the Auto Industry's Photo Headlight Dimmers.
  .......... Bob Ziolkowski, Apopka FL, 2nd of January 2015
  
  
• This method of current control was popular for post WWII radio receivers in the UK, due to the number of differing supply voltages being AC & DC in the same locality (some supplies actually switched between AC & DC at different times of the day). This was due to the damage inflicted on the supply companies by the blitz, a plethora of differing emergency local supplies being inaugurated to give some sort of power supply to the crippled network in many town and cities. The barretta was a simple way of making mains receivers universal for the differing power supplies where you would change the resistance value of the device depending on the voltage supply, and bypass the rectifier valve if the supply was DC. I bought my first valve radio set in 1986 for a pound at a boot fair,the make was PAN and it was manufactured in 1946 the barretta went open circuit some years later and a 60W light bulb was substituted until a replacement was found. The set still returns good service today
  .......... Mark J T Bowman, Strathfield NSW Australia, 27th of March 2011
  
  

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