Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1984-03-12
1986-12-30
Sloyan, T. J.
Communications: electrical
Audible indication
Percussion-type sound producer
364724, 375 12, 340347AD, 340347DA, 340347CC, 340347M, 379339, H03K 1302
Patent
active
046332251
ABSTRACT:
A circuit for generating a desired two terminal impedance at the two terminals by coupling analog signals appearing at the two terminals into an analog to digital converter, supplying the output therefrom to a digital processing circuit, leading the outputs therefrom to a digital analog converter, and connecting the output therefrom to the two terminals to form a feedback loop. The digital processing circuit processes using a desired transfer function. An analog processing circuit is provided which receives the analog signals appearing at said two terminals as input, and which passes the component of the signal having frequencies higher than the frequencies processed in the digital processing circuit. The output from the analog processing circuit is connected to the two terminals to form another feedback loop, and the component of higher frequencies is coupled to pass the analog processing circuit instead of the digital processing circuit to lower the frequencies to be processed in the digital processing circuit, thus enabling to use a less costly digital processing circuit.
REFERENCES:
patent: 4351060 (1982-09-01), Treiber
patent: 4488144 (1984-12-01), Wollman
Eckley et al, Digital Signal Solves Hybrid Balance Puzzle, Telephone Engineer & Management, Aug. 1, 1983, pp. 39. 40, 42, 44 and 45.
"Signal-Processing Chips Enrich Telephone Line-Card Architecture", by Russel Apfel et al, pp. 113-118, Electronics, May 5, 1982.
"Voice Signal Processing in Digital Local Exchanges", by Robert H. Lechner, 1983 IEEE, pp. 1566-1571.
Hayashi Toshio
Maeda Youichi
Nippon Telegraph and Telephone Public Corp.
Sloyan T. J.
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