Browse Prior Art Database

Full Duplex Data Transmission System

IP.com Disclosure Number: IPCOM000076573D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Dulany Jones, G: AUTHOR

Abstract

A digital bandpass filter for a single circuit full-duplex transmission system is shown.

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Full Duplex Data Transmission System

A digital bandpass filter for a single circuit full-duplex transmission system is shown.

The system uses two different frequency bands, one for each direction of transmission, and provides each receiver with a bandpass filter to allow only signals emanating from the other terminal to be processed.

Digital data to be transmitted controls a frequency-shift keying (FSK) transmitter 11 to supply to a line driver 43, two distinct frequency signals in a narrow frequency band, e.g. 1070 Hz and 1270 Hz for "0" and "1" data bits, respectively. These signals are passed through a junction 13 to a communication line 14. Data will be received from line 14 at junction 13 in a different frequency band, e.g. 2025 Hz and 2225 Hz for 0 and 1 data bits, respectively. A time-delay band separation filter 19 will remove the transmitted signals and will pass the receiving. signals to a frequency discriminator 96-97.

The system is driven by an oscillator 31 operating at 321.0 KHz. The FSK transmitter comprises a counter 37 driven from clock output 34. AND 38 provides an output signal to OR 40 when counter 37 reaches a count of 63, and AND 39 provides an output signal to OR 40 while counter 37 stands at count 75. Flip- Flop 42 provides an output signal which is a square wave, at a frequency corresponding to the signal level then present on line 10. Counter 37 will be reset by a latch circuit (inverter 50, NOR 52 and 54) at the next transition of the c...