Browse Prior Art Database

Data Transmission Subsets

IP.com Disclosure Number: IPCOM000096224D
Original Publication Date: 1963-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Horgan, TB: AUTHOR

Abstract

This hybrid data transmission subset exploits the unique features of an FM limiter with positive feedback of such magnitude that selfoscillation occurs. In the absence of an input signal, the selfoscillation frequency captures the limiter and causes line interference to be rejected. Upon application of a proper input signal, the oscillation conditions are destroyed, and the transmitted signal captures the limiter.

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Data Transmission Subsets

This hybrid data transmission subset exploits the unique features of an FM limiter with positive feedback of such magnitude that selfoscillation occurs. In the absence of an input signal, the selfoscillation frequency captures the limiter and causes line interference to be rejected. Upon application of a proper input signal, the oscillation conditions are destroyed, and the transmitted signal captures the limiter.

The over all system (A) is similar to usual two-tone FSK (frequency shift keyed) with limiter, but has important advantages. First, the transmitting oscillator is simply keyed on and off, rather than shifted between two frequencies. On the transmission channel, equivalent signalling speeds are achieved in less band width because of the elimination of the wasted zone between the two frequencies in conventional methods. Receiver equipment is considerably simplified. First, the prefilter used to sort tones in a parallel data subset must exhibit only single response peaks. Twin peaks are required in FSK. Secondly, because the positive feedback around a limiter is realized as two individual filters, one tuned to the self-oscillation frequency and the other tuned to the keyed transmission frequency, the detection decision is accomplished by differential comparison of the signal amplitudes across the two filter tanks. In the usual FSK, the two tones are usually close together in the spectrum, requiring very steep edge filters to separate them. In this set, the rest frequency is chosen typically three to five octaves removed from the transmission frequency. By realizi...