ces (e.g., subminiature hear- ing aid tubes) and potting compounds were tested. In 1954, Signal Corps liai- son official G. D. Bagley was able to obtain approximately 100 of the Western Electric type 1760 transistors (the first available outside BTL) for use by JPL engineer Bill Sampson in the construction of a PN generator. The resulting circuitry was an interesting combination of distributed-constant delay lines and transistor amplifiers and logic, chosen because it minimized the number of active elements required [169]. This general method of con- struction remained the norm at JPL through 1958. Late in 1954, a separate group under Sampson was formed for the pur- pose of investigating possible countermeasures against the SCW system equipment designed by a group headed by Walt Victor. Created to make this phase of the program as objective as possible, this organization brought forth Early Spread-Spectrum Systems a thoroughly designated system with high countermeasures immunity. Here are three issues on which significant progress was made. 1. It was hoped that repeater jamming would be ineffective as a result of the high TOA resolution capability of SS and the excess propagation delay incurred by the repeater. The period of the PN sequence was made longer than the missile flight time SO that it would be impossible for a repeater to store a PN coded signal for nearly a full period and deliver it to the victim receiver in synchronism with the directly transmitted PN sequence one period later. A weakness in this regard still existed in a simple m-sequence generator based on a linear recursion. Specifically, these sequences possessed a "cycle-and-add" property (see Chapter 5, Section 5.4.2) by which the modulo 2 sum of a sequence and a delayed version of that sequence results in the production of the same sequence at still another delay. The equivalent "shift-and-multiply" property for the 1 version of these m-sequences, satisfying the equation quoted ear- lier in this subsection, conceivably could be used by a jamm