Patent US4076971A successfully refreshed from Google Patents.
US4076971A
Expired / Lapsed
US
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Subscriber line testing system
Assignee: Hitachi Ltd
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Filing: 1976-09-08
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Granted: 1978-02-28
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Expires: 1996-09-08
Abstract
Abstract A testing system for testing an impedance of a subscriber line by connecting a test circuit to the subscriber line through one of channels in a network including current self-holding semiconductor switching devices, wherein a series circuit of a second channel and a constant current source is connected in parallel with said first-mentioned channel whereby the current self-holding semiconductor switching devices in said first and second channels are kept conductive by said constant current source.
Inventors
- 👤 Takuji Mukaemachi
- 👤 Yutaka Fukushima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:17
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/22; H04M3/26; H04M3/28; H04M3/30
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
102 words
A subscriber line testing system comprising: a. a channel network having a first channel including a line terminal, first and second trunk terminals and at least one current self-holding semiconductor switching device connecting said line terminal with said first trunk terminal, and a second channel including at least one current self-holding semiconductor switching device for connecting said line terminal with said second trunk terminal; b. a subscriber line connected to said line terminal; and c. a line test trunk including a floating current source connected to said first and second trunk terminals and a test circuit connected to said second trunk terminal.
Claim 2
Dependent Claim
102 words
A subscriber line testing system comprising: a. a channel network having a first channel including a line terminal, first and second trunk terminals and at least one current self-holding semiconductor switching device connecting said line terminal with said first trunk terminal, and a second channel including at least one current self-holding semiconductor switching device for connecting said line terminal with said second trunk terminal; b. a subscriber line connected to said line terminal; and c. a line test trunk including a floating current source connected to said first and second trunk terminals and a test circuit connected to said second trunk terminal.
Claim 3
Dependent Claim
40 words
A subscriber line testing system according to claim 1, wherein said second channel is an interruption channel to the subscriber, which interruption channel provides a connecting path for establishing double connections between a talking subscriber and a test subscriber line.
Claim 4
Dependent Claim
31 words
A subscriber line testing system according to claim 2, wherein said interruption channel is a test vertical of a prescribed switch with accomodates a talking subscriber for establishing an interruption connection.
Claim 5
Dependent Claim
55 words
A subscriber line testing system according to claim 1 wherein said test circuit of the line test trunk includes a resistor having its one end connected to said second trunk terminal, a D.C. power supply connected to the other end of said resistor, and a measuring circuit connected to said one end of said resistor.
Claim 6
Dependent Claim
74 words
A subscriber line testing system according to claim 1 wherein said test circuit of said line test trunk includes a resistor having its one end grounded through a D.C. power supply, a capacitor having its one end grounded, a switching contact for selectively connecting the other end of either one of said resistor and said capacitor to said second trunk terminal, and a voltage measuring circuit connected to said one end of said capacitor.
Claim 7
Dependent Claim
24 words
A subscriber line testing system according to claim 1 wherein said test circuit is a current measuring circuit connected to said second trunk terminal.
Claim 8
Dependent Claim
35 words
A subscriber line testing system according to claim 1 wherein a voltage compensation means for compensating for a voltage drop in said second channel is provided between said second trunk terminal and said test circuit.
Claim 9
Dependent Claim
54 words
A subscriber line testing system according to claim 7 wherein said voltage compensation means includes a parallel circuit of a semiconductor device having a similar forward voltage drop to that of the semiconductor switching device in said second channel and a second constant current source for feeding a forward current through said semiconductor device.
References Cited (Backward Citations)
US3891838A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-02-27 | 1981-08-29 | 1982-02-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-02-27 | 1985-08-29 | 1986-02-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-02-27 | 1989-08-29 | 1990-02-28 | $7700.00 | Window Closed / Lapsed |