US4175216A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intercom calling apparatus in a key telephone system
Assignee: Iwatsu Electric Co Ltd
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Filing: 1978-04-17
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Granted: 1979-11-20
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Expires: 1998-04-17
Abstract
Abstract An intercom calling apparatus in a key telephone system including a page switch for switching the transmitter from a talking circuit network to an intercom calling path while a contemporaneous call on a central office line is held by the series combination of a resister and a varistor forming a parallel circuit with the transmitter in the talking circuit network.
Inventors
- 👤 Gunzo Kita
- 👤 Koichi Sekiguchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 20:29
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/08; H04M1/00; H04M1/02; H04M1/11; H04M1/12; H04M11/00; H04M11/02; H04M11/022; H04Q; H04Q3/00
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
162 words
In a key telephone system wherein a plurality of key telephone sets are connected to a central office via a central office line, each of said key telephone sets having a transmitter, a talking circuit network, and a loudspeaker circuit for signalling an intercom call, and wherein each of said loudspeaker circuits signals said intercom call, an intercom calling apparatus comprising: a two-position page switch; means for electrically connecting the transmitter to the talking circuit network when the page switch is in a first position; means for electrically connecting the transmitter to the loudspeaker circuit in each of said key telephone sets when the page switch is in a second position; and means for holding the connection of the talking circuit network with a central office line by a series combination of a resistor and a varistor forming a parallel circuit with the transmitter in the talking circuit network at the same time the page switch is changed to the second positon.
Claim 2
Dependent Claim
162 words
In a key telephone system wherein a plurality of key telephone sets are connected to a central office via a central office line, each of said key telephone sets having a transmitter, a talking circuit network, and a loudspeaker circuit for signalling an intercom call, and wherein each of said loudspeaker circuits signals said intercom call, an intercom calling apparatus comprising: a two-position page switch; means for electrically connecting the transmitter to the talking circuit network when the page switch is in a first position; means for electrically connecting the transmitter to the loudspeaker circuit in each of said key telephone sets when the page switch is in a second position; and means for holding the connection of the talking circuit network with a central office line by a series combination of a resistor and a varistor forming a parallel circuit with the transmitter in the talking circuit network at the same time the page switch is changed to the second positon.
Claim 3
Dependent Claim
46 words
The intercom calling apparatus recited in claim 1, wherein the connecting means to the loudspeaker comprises: an intercom calling path having a d.c. power source for activating the transmitter; and means for picking up a voice signal in the intercom calling path to energize the loudspeaker.
Claim 4
Dependent Claim
19 words
The intercom calling apparatus as recited in claim 2, wherein the voice signal picking up means comprises: a transformer.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-11-19 | 1983-05-21 | 1983-11-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-11-19 | 1987-05-21 | 1987-11-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-11-19 | 1991-05-21 | 1991-11-20 | $7700.00 | Window Closed / Lapsed |