US4608464A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interface circuit interconnecting a bidirectional two-wire line with unidirectional four-wire lines
Assignee: Hitachi Ltd
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Filing: 1984-05-01
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Granted: 1986-08-26
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Expires: 2004-05-01
Abstract
Abstract In an interface circuit which couples a two-wire line of bidirectional transmission and unidirectional four-wire receiving and transmitting lines; in order to permit the interface circuit to operate in adaptation to the fluctuation of an impedance with the two-wire line side viewed from the four-wire receiving line, the four-wire receiving line is provided with a plurality of filters and a group of switches for selecting the filters, an output of the four-wire transmitting line is compared with outputs obtained by scanning the filters, and the filter providing the minimum output difference in the comparisons is selected and connected.
Inventors
- 👤 Yuichi Morikawa
- 👤 Hirohiko Sato
- 👤 Eiichi Amada
- 👤 Toshiro Suzuki
- 👤 Hirotoshi Shirasu
- 👤 Hiroshi Kuwahara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 01:19
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/03; H04B3/20; H04B3/23
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
191 words
An interface circuit for coupling a two-wire line with a four-wire line having a receiving line and a transmitting line to prevent a signal received from the receiving line from being transmitted to the transmitting line, comprising: a buffer amplifier having an input coupled to said receiving line and an output coupled to said two-wire line through a terminal impedance; a first and a second subtractor each of which has a first input coupled to said two-wire line and a second input, one of the subtractors having an output coupled to the transmitting line; a group of filters to be selectively connected between said output of said buffer amplifier and said second input of said first and second subtractors; filter selection means for selectively coupling a pair of filters from among said group of filters, respectively, to the second inputs of said first and second subtractors; and filter controller means for comparing the outputs of said first and second subtractors and for controlling said filter selection means so as to finally select a filter to minimize the leakage of a signal from said four-wire receiving line to said four-wire transmitting line.
Claim 2
Dependent Claim
191 words
An interface circuit for coupling a two-wire line with a four-wire line having a receiving line and a transmitting line to prevent a signal received from the receiving line from being transmitted to the transmitting line, comprising: a buffer amplifier having an input coupled to said receiving line and an output coupled to said two-wire line through a terminal impedance; a first and a second subtractor each of which has a first input coupled to said two-wire line and a second input, one of the subtractors having an output coupled to the transmitting line; a group of filters to be selectively connected between said output of said buffer amplifier and said second input of said first and second subtractors; filter selection means for selectively coupling a pair of filters from among said group of filters, respectively, to the second inputs of said first and second subtractors; and filter controller means for comparing the outputs of said first and second subtractors and for controlling said filter selection means so as to finally select a filter to minimize the leakage of a signal from said four-wire receiving line to said four-wire transmitting line.
Claim 3
Dependent Claim
86 words
An interface circuit in accordance with claim 1 wherein: (a) the group of filters consists of more than two filters; and (b) the filter selection means sequentially selects a different pair of filters after each comparison by the filter controller means with one of the pair of selected pair of filters for each comparison after a first comparison being one of the filters selected from a previous comparison which produced a minimum leakage of a signal from said four-wire receiving line to said four-wire transmitting line.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-08-25 | 1990-02-24 | 1990-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-25 | 1994-02-24 | 1994-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-25 | 1998-02-24 | 1998-08-26 | $7700.00 | Window Closed / Lapsed |