Patent US3920902A successfully refreshed from Google Patents.
US3920902A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Off-premises station line circuit for a key telephone system
Assignee: NEC Platforms Ltd
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Filing: 1973-04-05
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Granted: 1975-11-18
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Expires: 1993-04-05
Abstract
Abstract Electrical apparatus for use in a key telephone system to enable connection of a non-key telephone set at a nearby or remote offpremises location to one or more of the key telephone sets in the system via the key system intercommunication circuits.
Inventors
- 👤 Kazuaki Matsuo
- 👤 Stephen E Kerman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 07:34
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/002
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
160 words
Key service unit apparatus for enabling intercommunication between a non-key telephone set and at least one key telephone set in a key telephone system, by use of at least one intercom line circuit connected to said key service unit, comprising, in combination, input and output terminal means; means, including at least one normally released first relay for automatically testing and connecting to said intercom line circuit when said circuit is idle, and for preventing establishment of a connection in response to a line busy status indication from said tested intercom line circuit; means, including a normally released second relay operated by an off-hook condition at said non-key telephone set, for establishing an intercom line testing path through said first relay, and for supplying signals, representative of dial pulses generated at said non-key telephone set to said selected idle intercom line; and means, including make contacts of said first and second relays, for electrically connecting said input and output terminal means.
Claim 2
Dependent Claim
160 words
Key service unit apparatus for enabling intercommunication between a non-key telephone set and at least one key telephone set in a key telephone system, by use of at least one intercom line circuit connected to said key service unit, comprising, in combination, input and output terminal means; means, including at least one normally released first relay for automatically testing and connecting to said intercom line circuit when said circuit is idle, and for preventing establishment of a connection in response to a line busy status indication from said tested intercom line circuit; means, including a normally released second relay operated by an off-hook condition at said non-key telephone set, for establishing an intercom line testing path through said first relay, and for supplying signals, representative of dial pulses generated at said non-key telephone set to said selected idle intercom line; and means, including make contacts of said first and second relays, for electrically connecting said input and output terminal means.
Claim 3
Dependent Claim
153 words
Apparatus according to claim 1 wherein a plurality of said intercom line circuits are provided further comprising means, including a plurality of additional relay means, provided in one-to-one correspondence with said intercom line circuits, for testing said plurality of and connecting to one of said plurality of intercom line circuits, when one or more of said circuits are idle, and for preventing connection thereto in response to busy status indications from said plurality of intercom line circuits; and further wherein said means, including said normally released second relay means, is additionally for establishing an operating current path to said plurality of additional relay means, the enumerated means being so proportioned and the combination being so constructed and arranged that said non-key telephone set has access through said key service unit apparatUs to any one of said plurality of intercom line circuits whenever any one or more of said intercom line circuits are idle.
Claim 4
Dependent Claim
67 words
Apparatus according to claim 2 additionally comprising further means, including a normally released relay responsive to an incoming call indication signal from one of said intercom line circuits, for establishing an operating path to said plurality of additional relay means, thereby operating the one of said additional relay means corresponding to the one of said plurality of intercom line circuits on which the call is being originated.
Claim 5
Dependent Claim
64 words
Apparatus according to claim 3 in which each of said plurality of additional relay means comprise two windings on a common core connected in mutual opposition so that each of said additional relay means can be operated in response to an idle indication from its corresponding intercom line circuit, and prevented from operating in response to a busy indication from said intercom line circuit.
References Cited (Backward Citations)
US2458262A
Cited
US2644041A
Cited
US2814675A
Cited
US3535461A
Cited
US3521004A
Cited
US3604857A
Cited
US3665112A
Cited
US3701855A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |