Did You Know...
...Chester Carlson was a patent agent who tired of having to make multiple copies of patent applications using the only duplication method available at the time: carbon paper. In 1959 he came up with a new copying system and took it to IBM for evaluation. The "experts" at IBM determined potential sales to be only 5,000 units because people wouldn't want to use a bulky machine when they had carbon paper. Carlson's invention was the xerography process, the company founded on the system is Xerox.
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US Patent 5289538 - Circuit arrangement for signal and information conversion between analog junction lines and digital terminal devices in communications exchanges
US Patent Issued on February 22, 1994
Estimated Patent Expiration Date:
March 14, 2011Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
Estimated Patent Expiration Date:
March 14, 2011Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.AbstractA circuit arrangement converts signals and information between analog junction lines and digital terminal devices in communications exchanges. A decentralized control device is provided in order to process and pass on switching criteria and codes received and sent to the respective analog junction line, inside and outside the audio frequency band, the circuit arrangement including a plurality of line interfaces, each coupled directly to a respective one of the decentralized control devices, for the switching criteria and codes to be exchanged outside of the audio frequency. At least one digital signal processor is provided for processing the codes to be exchanged within the audio frequency band, the digital signal processor being looped in via a hybrid connection and converter in a speech path which cooperates with the control device. A digital terminal interface is responsive to the control device and the signal processor, the digital terminal interface being modulated by the control device and the signal processor to provide a plurality of useful channels and at least one signaling channel. | InventorsAssigneeApplicationNo. 669487 filed on 03/14/1991US Classes:379/402, Hybrid circuit379/339, With signal conversion (e.g., dial to DTMF, analog to PCM)379/399.02Circuitry to provide a coder and decoder functionField of Search379/402, Hybrid circuit379/338, REPEATER (E.G., VOICE FREQUENCY)379/339, With signal conversion (e.g., dial to DTMF, analog to PCM)379/344, Component processes bidirectional signals379/345Including two-to-four wire conversion or hybrid circuitExaminersPrimary: Dwyer, James L.Assistant: Shehata, M. Attorney, Agent or FirmUS Patent References4110560, Communication apparatusIssued on: 08/29/1978 Inventor: Leary , et al.4270027, Telephone subscriber line unit with sigma-delta digital to analog converter Issued on: 05/26/1981 Inventor: Agrawal , et al.4456991, Telephone line circuit and system Issued on: 06/26/1984 Inventor: Chea, Jr. , et al.4759059, Analog telephone circuit for digital telephone system Issued on: 07/19/1988 Inventor: Christensen4852160, Channel unit interface circuit Issued on: 07/25/1989 Inventor: Kiko , et al.4894864, Interface circuit Issued on: 01/16/1990 Inventor: Cook5133006, Combination interface circuit for coupling a digital loop carrier telephone system Issued on: 07/21/1992 Inventor: Khuat5151936Interface means Issued on: 09/29/1992 Inventor: Riedle Foreign Patent References
International ClassH04M 003/00Foreign Application Priority Data1990-03-16 DE |
