 (Industrial Development Engineering Associates) of Indianapolis, Indiana, which was the first practical transistor radio.The TR-1 was announced on October 18, 1954 and put on sale in November 1954 for US$49.95 (the equivalent of about US$361 in year-2005 dollars) and sold about 150,000 units.The TR-1 used four Texas NPN transistors and had to be powered by a 22.5-volt battery, since the only way to get adequate radio frequency performance out of early transistors was to run them close to their collector-to-emitter breakdown voltage.