Two British suppliers offer devices for producing HT voltage from low-voltage sources.

• EDS makes a DC to DC converter that produces 90V from six 1.2V rechargeable cells. For details send SAE to EDS, 27 The Templars, Worthing, BN14 9JT.
• TRACKTEK SYSTEMS Ltd offers a range of converters for military and domestic radio sets that should meet practically all needs. Starting with a standard 12V input, their various products offer outputs at 1.5-2.5V, 3V, 4.5V, 6V, 12V, 67.5V, 90V, 120V, 150V and 180V. Negative voltages are also possible. For information send SAE to Tracktek Systems Ltd, P.O. Box 45, Hitchin, SG5 2AH.