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This paper summarizes two high-speed, adaptive modems for voice-band channels. The first is a 4800 bps, MOS/LSI modem which is almost entirely contained on 5 to 8 MOS/LSI chips, depending upon the version. The second modem is experimental and employs advanced, novel techniques for automatic equalization, carrier recovery, timing recovery, and jitter correction. Partial response, SSB signaling provides both high bandwidth efficiency and error correction without digit redundancy. Measured performance curves, including bit error rates, show that, under various transmission conditions, this modem provides outstanding performance. Implementation on a few MOS/ LSI chips or in an inexpensive signal processor is feasible.

The Army for some time has considered the feasibility of transmitting digital information over tactical narrowband FM. This paper presents the results of bit error rate measurements made on narrowband FM links being interfered with by a variety of modulation types. The desired signal is a frequency shift keying signal of 1200 and 2400 Hertz with bit rates of 600 and 1200 bits per second. This signal is transmitted over a 25 kHz FM channel. The interfering signals will be: a. Gaussian noise b. ASK 1200 and 2400 Hertz tones at 600 bits per second c. ASK 1200 and 2400 Hertz tones at 1200 bits per second d. ASK 750 and 1500 Hertz tones at 750 bits per second e. Narrowband voice f. AM noise.