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to take 01010101 from the eight-bit table, 0101 from the four-bit table, and 01 from the two-bit table and construct a new table. From a six-bit table we could use 010101. All of these sequences are orthogonal to each other when substituted into Equation 3. Also, the alternating ZeYo and one code may be taken from higher order tables in constructing this new table. Pulse frequency modulation does exactly this in constructing a code. The code is made up of alternating zeYos and ones taken from higher order codes. For PFM signals in the frequency range from 5 to 15 kc, the 5.0 kc sequence would be 100 bits of 50 zeyos and 50 ones in an alternating pattern; the 5.1 kc sequence would be 102 bits in this same alternating pattern. Table 4 is such a table. Each frequency contains an integral number of cycles because the pulse length, derived from Equation 3, is constant. The
12