US3794932A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Vital level detector
Assignee: Trane US Inc
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Filing: 1972-04-26
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Granted: 1974-02-26
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Expires: 1992-04-26
Abstract
Abstract This disclosure relates to a fail-safe level detecting circuit including a solid state amplifier having a feedback loop. The feedback loop includes a frequency determining twin-tee network and a voltage breakdown device. The amplifier produces a.c. oscillations when and only when the level of a d.c. voltage exceeds the threshold value of the voltage breakdown device.
Inventors
- 👤 R Grundy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 00:49
CPC Classifications
H; H03; H03B; H03B5/00; H03B5/20; H03B5/26
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
160 words
A fail-safe voltage level detector comprising, an amplifier having an input and an output circuit, a regenerative feedback loop connected between said input circuit and said output circuit of said amplifier, said feedback loop including a twin-tee network, a voltage responsive variable impedance device, a source of d.c. operating potential adapted to be connected across said voltage responsive variable impedance device, said twin-tee network having a capacitive leg connected to one end of said voltage responsive variable impedance device and having a resistive leg connected to the other end of said voltage responsive variable impedance device, said twin-tee network phase shifts a given frequency signal substantially a 180 degrees when and only when said d.c. operating potential source is capable of causing said voltage responsive variable impedance device to become conductive and to assume a low impedance condition so that said d.c. operating potential and a.c. feedback signals are supplied to said amplifier via said voltage responsive variable impedance device.
Claim 2
Dependent Claim
160 words
A fail-safe voltage level detector comprising, an amplifier having an input and an output circuit, a regenerative feedback loop connected between said input circuit and said output circuit of said amplifier, said feedback loop including a twin-tee network, a voltage responsive variable impedance device, a source of d.c. operating potential adapted to be connected across said voltage responsive variable impedance device, said twin-tee network having a capacitive leg connected to one end of said voltage responsive variable impedance device and having a resistive leg connected to the other end of said voltage responsive variable impedance device, said twin-tee network phase shifts a given frequency signal substantially a 180 degrees when and only when said d.c. operating potential source is capable of causing said voltage responsive variable impedance device to become conductive and to assume a low impedance condition so that said d.c. operating potential and a.c. feedback signals are supplied to said amplifier via said voltage responsive variable impedance device.
Claim 3
Dependent Claim
16 words
A fail-safe detector as defined in claim 1, wherein said amplifier is a multi-stage amplifying circuit.
Claim 4
Dependent Claim
25 words
A fail-safe detector as defined in claim 1, wherein said twin-tee network includes a plurality of resistors and capacitors connected in series and parallel relationship.
Claim 5
Dependent Claim
51 words
A fail-safe detector as defined in claim 1, wherein a pair of resistors connected in series and a capacitor connected to the resistor junction point form one tee network and a pair of capacitors connected in series and a resistor conNected to the capacitor junction point form the other tee network.
Claim 6
Dependent Claim
27 words
A fail-safe detector as defined in claim 4, wherein said voltage responsive variable impedance device is connected in series with said capacitor of said one tee network.
Claim 7
Dependent Claim
37 words
A fail-safe detector as defined in claim 4, wherein said amplifier includes a pair of cascaded transistors one of which is connected in a common-collector configuration and the other of which is connected in a common-emitter configuration.
Claim 8
Dependent Claim
21 words
A fail-safe detector as defined in claim 1, wherein said voltage responsive variable impedance device is a shunt connected Zener diode.
Claim 9
Dependent Claim
22 words
A fail-safe detector as defined in claim 1, wherein said voltage responsive variable impedance device is a shunt connected voltage breakdown diode.
Claim 10
Dependent Claim
54 words
A fail-safe detector as defined in claim 1, wherein the impedance of one leg of said twin-tee network is reduced when a predetermined value of d.c. potential is applied across said voltage responsive variable impedance device which is a shunt connected regulator so that sufficient feedback occurs and said amplifier produces a.c. output signals.
Claim 11
Dependent Claim
85 words
A fail-safe detector as defined in claim 1, wherein one leg formed by a first resistor and a first capacitor of said twin-tee network is connected to the collector electrode of a common-emitter output amplifier stage, a second leg formed by a second resistor and a second capacitor of said twin-tee network is connected to the base electrode of a common-collector input amplifier stage and a third leg formed by a third resistor and a third capacitor of said twin-tee network is connected to ground.
References Cited (Backward Citations)
US3660691A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |