TRANSISTOR MUSEUM™ Historic Transistor Photo Gallery
Transistor Size (1/2”H X 3/8”OD) Bottom View. Some Units Have Text: “Motorola EP-7” Stamped on Top of Case	MOTOROLA EP-7 PROTOTYPE TYPE Germanium Point Contact USAGE Experimental DATE INTRODUCED Early 1950s CASE STYLES Silver Metal AVAILABILITY Very Rare (Prototype)
HISTORIC NOTES The first transistors were known as point contact, a name derived from the fact that the collector and emitter connections of the transistor were formed using sharpened metal points, pressed into contact with the germanium base block. (See Bell Labs TYPE A Transistor for a detailed discussion). Point contact transistors had many problems, including mechanical and thermal instability, a high level of noise and poor manufacturability. Many companies experimented with making point contact devices, and some companies offered commercial versions in limited quantities. Motorola briefly experimented with point contact transistor technology in the early 1950s, before quickly moving on to become a major supplier of alloy junction germanium power transistors in the late 1950s. The EP-7 units shown above are experimental point contact transistors developed by Motorola in the early 1950s. These devices appear to be hand-built. Note the plug of solder on the side of the case in each unit shown above. This technique was likely used to cover a hole that was required to allow physical adjustment of the point contacts to achieve best performance. There is no record of Motorola point contact transistors being offered for commercial sale.
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