The author devised the name "transistor" in may 1948 when W. Brattain asked him for a suitable name. The early transistor was the dual of a vacuum tube and as such would have transresistance; this suggested the name. Some historical aspects concerning the development of the transistor are discussed.

Previous work has shown that the capacity of the single-mode photon-counting channel in the region in which quantum effects are most pronounced is1/(kT \ln 2)bit/J. HereTis the quantum noise temperature, andkis Boltzmann's constant. However, to achieve this, the number of photons per second must be very low, so this does not determine the capacity of the average power-limited photon channel in bits per second. Here the previous work is extended and the capacity is determined in bits per second. This includes a determination of the optimum counting time. The capacity in bits per second is for lowTasymptotic toP_{s}/(kT \ln 2), whereP_{s}is the average signal power. This is high enough to suggest that photon counting be seriously considered for applications such as a deep space to near Earth link. Some related problems are also considered including a peak power limitation.

For a constant added noise density at high signal-to-noise ratios and for the same error rate, three-phase PSK requires about 0.75 dB less energy per bit than two-phase or four-phase PSK. However, at very low signal-to-noise ratios, three-phase PSK requires about 0.74 dB more energy per bit of channel capacity than two-phase or four-phase PSK.

In optical communication, ideal amplification of the received signal leads to a limiting signaling rate of 1 nat per photon. This is much inferior to the optimum limit ofkTjoules/nat, which we can theoretically approach by counting photons. Practically, the rates we can attain by photon counting will be limited by how elaborate codes we can instrument rather than by thermal photons.

Shannon's communication (information) theory cast about as much light on the problem of the communication engineer as can be shed. It reflected or encompassed earlier work, but it was so new that it was not really understood by many of those who first talked or wrote about it. Most of the papers published on information theory through 1950 are irrelevant to Shannon's work. Later work has given us useful information and encoding schemes as well as greater rigor, but the wisdom of Shannon's way of looking at things and his original theorems are of primary importance.

In digital transmission of binary (+1,-1) signals it is desirable that the stream of pulses which constitutes the signal have no dc, that is, that the power spectrum go to zero at zero frequency. It is desirable that, for a given efficiency or entropy, the spectrum rise slowly with increasing frequency. We have obtained the spectrum for selected blocks with equal numbers of plus ones and minus ones. For a given efficiency, this is better than the spectrum obtained by Rice, using the Monte Carlo method, for block encoding using polarity pulses. An algorithm given by Schalwijk should allow simple encoding into selected blocks.

The switching of addressed blocks of data through a network (message switching) is particularly suited to the sort of inquiry-response communication characteristic of many business transactions. In a system of interconnected loops, efficient message switching can be attained with distributed control rather than common control. The initial capital investment in such a system would be low and the investment would grow only as the system grew.

One ofMfrequency translates of a common signal is sent over a fading channel and is received in additive white noise. The receiver decides which signal was sent using energy measurements only. It is shown that asMis allowed to become very large, the performance depends only on the probability distribution of received energy per bit, and that this limiting behavior is the same as for optimum detection based on full knowledge of instantaneous channel properties. If sufficiently many independent copies of the channel can be achieved (i.e., independent diversity branches), the performance can be made to approach as closely as desired that of the nonfading infinite-bandwidth channel, independently of the exact channel statistics.