tered by a reconnaissance receiver trying to detect it. RACEP: Standing for Random Access and Correlation for Extended Performance, RACEP was the name chosen b the Martin Company to describe their asynchronous discrete address system that provided voice ser- vice for up to 700 mobile users [164]. In this system, the voice signal was first converted to pulse position modulation, and then each pulse in the resul- tant signal was in turn converted to a distinctive pattern of three narrow pulses and transmitted at one of a possible set of carrier frequencies. With the patterns serving also as addresses, this low duty cycle format possessed some of the advantages of SS systems. Branches on the SS Tree 500/us DELAY SEQUENCE PROGRAMMER POLARITY POLARITY POLARITY SWITCH SWITCH SWITCH POLARITY TRANSMITTER SWITCH 500/LS 500/us SPACE CONTROLLER SEQUENCE PROGRAMMER 500us DELAY LINE POLARITY POLARITY POLARITY MIXER LIMITING SWITCH SWITCH SWITCH LOCAL OSCILLATOR MARK-SPACE 1 DETECTOR OUTPUT Figure 2.29. Costas and Widmann's Phantom system employs a pulsed delay line with pseudorandomly controlled taps summed to provide an SS signal for modulation. An identically structured system with a synchronous replica of the tap controller is used to construct a matched pseudorandom filter for data detection at the receiver. (Diagrams modified from [192].) The Historical Origins of Spread-Spectrum Communications Cherokee: Also by the Martin Company, this was a PN system with a trans- mission bandwidth of nearly a megahertz and a processing gain of about 16 dB [164]. Both RACEP and Cherokee were on display at the 15th Annual Convention of the Armed Forces Communications and Electronics Association in June 1961. MUTNS: Motorola's Multiple User Tactical Navigation System was a low frequency, hyperbolic navigation system employing PN signalling. Navigation was based on stable ground wave propagation with the SS modulation used to discriminate against the skywave, as it was in Sylvania's WHYN. Motorola, a subcontractor to JPL on the Jupiter CO