What is smallest transistor radio?

The smallest transistor radio was the Regency TR-1, introduced in 1954. It measured only 3.5 inches by 2 inches by 1.25 inches and weighed just 12.5 ounces. The TR-1 was the first commercially successful transistor radio and was a major breakthrough in radio technology. The radio was powered by a single 22.5-volt battery and had four transistors, which replaced the bulky vacuum tubes used in earlier radios. The TR-1 had a range of about five miles and cost $49.95 (equivalent to around $485 today). Despite its high price, the TR-1 was a huge success and sold over 150,000 units in its first year on the market.