reselling circuits that kept TELPAK's fictitious pipes from being, on average, particularly full. The Disruptive Transistor Other than a few private microwave systems, the 1960s saw little pressure on the monopoly. But all was not well: Technological progress was creating new demands on the network, as well as new sources of supply for potential competi- tors. Key to this was a Bell Labs invention-the transistor-that was worth far less to AT&T than to the rest of the world. We do not think much about the humble transistor nowadays. We tend to think instead about products that contain thousands or millions of them, for example, very large scale integration (VLSI) chips such as microprocessors and Ma Bell and Her "Natural Monopoly, 1876-1969 memories. But these complex semiconductors trace their origins back to 1947's epic discovery that a small current properly applied to a semiconductor crystal can cause a large change in the current passing through it. The original transis- tors were used as substitutes for the then-ubiquitous vacuum tube, first in size- sensitive applications such as hearing aids, and later, as the price fell, in con- sumer products such as hand-held radios. (In consumer parlance of the 1960s, the word "transistor" was often used to refer to a transistor radio, typically a hand-held low-fidelity AM model.) But it was in the fledgling computer indus- try that transistors arguably had their biggest impact. Even a simple digital com- puter of the early 1950s needed thousands of vacuum tubes, each consuming several watts of electricity to run its filaments, thus using huge amounts of power and generating vast amounts of heat in the process. The market for room-sized tube computers was small. Transistors enabled computers to be smaller, faster, cooler, and cheaper. While few businesses owned a computer in 1955, they were commonplace by 1965. Even in those early days, it was clear that computers needed to communi- cate: For one thing, users generally sat at terminals some distance from the "glass hou