US3750098A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Downhole acoustic logging control system
Assignee: Schlumberger Technology Corp
•
Filing: 1970-11-13
•
Granted: 1973-07-31
•
Expires: 1990-11-13
Abstract
Abstract Apparatus for acoustically logging a borehole to obtain indications of the effectiveness of the cement between a casing and a borehole to prevent fluid communication characterized by a downhole digital control system for repetitively energizing an acoustic transmitter and selectively coupling electrical signals developed by the receivers upon receiving transmitted acoustic energy to a signal channel. The signal channel is arranged to provide at least two degrees of amplification of the electrical signals in a sequence synchronized with the transmissions of acoustic energy from the transmitter. In a predetermined order, electrical signals from each receiver corresponding to different acoustic transmissions will be amplified to respective different degrees and coupled to a conductor for transmission to the surface. For the purpose of identifying the receiver and degree of amplification selected, the system provides, at preselected intervals, both an identifying pulse signal and a calibration signal of reference amplitude and frequency. All functions of the downhole system are controlled by a digital sequence counter and associated circuits which automatically select the receiver, the degree of amplification and relative time of occurrence of each signal during each sequence.
Inventors
- 👤 F Zill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 05:54
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/40; G01V1/44; G01V1/46
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
159 words
In apparatus for acoustically logging a borehole including a casing cemented in a borehole to obtain indications concerning the cement bonding, a downhole signal transmission system, comprising: a logging tool movable through the borehole, including at least one transmitter for sending acoustic energy through the borehole and casing and at least one receiver spaced from the transmitter for developing an electrical signal in response to each transmission of acoustic energy received thereby; means for repetitively energizing the transmitter at preselected time intervals to effect corresponding repetitive transmissions of acoustic energy; means coupled to the receiver for amplifying each such electrical signal; means for coupling the amplified signals to a conductor for transmission to the earth''s surface; and means synchronized with the transmissions of acoustic energy for sequentially controlling the degree of amplification of each such electrical signal by the amplifying means to obtain in each given sequence at least two electrical signals which have been amplified to different degrees.
Claim 2
Dependent Claim
159 words
In apparatus for acoustically logging a borehole including a casing cemented in a borehole to obtain indications concerning the cement bonding, a downhole signal transmission system, comprising: a logging tool movable through the borehole, including at least one transmitter for sending acoustic energy through the borehole and casing and at least one receiver spaced from the transmitter for developing an electrical signal in response to each transmission of acoustic energy received thereby; means for repetitively energizing the transmitter at preselected time intervals to effect corresponding repetitive transmissions of acoustic energy; means coupled to the receiver for amplifying each such electrical signal; means for coupling the amplified signals to a conductor for transmission to the earth''s surface; and means synchronized with the transmissions of acoustic energy for sequentially controlling the degree of amplification of each such electrical signal by the amplifying means to obtain in each given sequence at least two electrical signals which have been amplified to different degrees.
Claim 3
Dependent Claim
81 words
AppaRatus according to claim 1, further comprising: a second receiver spaced from the transmitter and first receiver for developing in a like manner an electrical signal in response to each transmission of acoustic energy received thereby; switch means connected to the first and second receivers for selecting at least one electrical signal from each receiver for passage to the amplifying means; and means synchronized with the transmission of acoustic energy for controlling the selection of electrical signals by the switch means.
Claim 4
Dependent Claim
30 words
Apparatus according to claim 2, in which: the switch control means is operative to connect at least one electrical signal from each receiver to the amplifying means during each sequence.
Claim 5
Dependent Claim
40 words
Apparatus as defined in claim 3, in which: the switch control means and sequential control means operate in synchronized order to provide sequentially to the conductor two signals from each receiver at respective said degrees of amplification during each sequence.
Claim 6
Dependent Claim
53 words
Apparatus according to claim 1, further comprising: means for generating a timing pulse in substantially simultaneous synchronization with each transmission of acoustic energy, the timing pulse having a characteristic separable from the electrical signals from the amplifying means; and means for coupling the timing pulse to the conductor for transmission to the surface.
Claim 7
Dependent Claim
143 words
A logging tool for acoustically logging a cased borehole and including: means for emitting and detecting acoustic energy in a borehole and for generating first electrical signals representative of the time of emission of acoustic energy and for generating second electrical signals representative of the waveform of detected acoustic energy; means for repetitively acutating said emitting means at preselected time intervals defining a signal processing sequence; means for detecting radiation emanating in a borehole and providing third electrical signals representative of the detected radiation; means for detecting couplings in a well casing and providing fourth electrical signals representative of the detection of such couplings; and means for sequentially transmitting to the surface said first, second, third and fourth signals during each time interval, including means for varying an electrical characteristic of one of said signals during at least one of said time intervals.
Claim 8
Dependent Claim
143 words
A logging tool for acoustically logging a cased borehole and including: means for emitting and detecting acoustic energy in a borehole and for generating first electrical signals representative of the time of emission of acoustic energy and for generating second electrical signals representative of the waveform of detected acoustic energy; means for repetitively acutating said emitting means at preselected time intervals defining a signal processing sequence; means for detecting radiation emanating in a borehole and providing third electrical signals representative of the detected radiation; means for detecting couplings in a well casing and providing fourth electrical signals representative of the detection of such couplings; and means for sequentially transmitting to the surface said first, second, third and fourth signals during each time interval, including means for varying an electrical characteristic of one of said signals during at least one of said time intervals.
Claim 9
Dependent Claim
45 words
Apparatus according to claim 1, further comprising: means for producing an electrical calibration signal having a preselected amplitude; and gating means for periodically coupling the calibration signal to the conductor during time periods exclusive of the presence of the amplified electrical signals on the conductor.
Claim 10
Dependent Claim
20 words
Apparatus as set forth in claim 7, in which: the calibration signal is a periodic waveform of fixed predetermined frequency.
Claim 11
Dependent Claim
39 words
Apparatus according to claim 8, further comprising: second gating means connected intermediate the receiver and the amplifying means for connecting each electrical signal to the amplifying means for a limited period of time following each transmission of acoustic energy.
Claim 12
Dependent Claim
54 words
Apparatus according to claim 1, further comprising: means for generating a signal indicative of the presence of a coupling between adjacent sections of the borehole casing, and means responsive to the sequential control means for coupling said pulse to the conductor in time displaced relation to the connected electrical signal during each time interval.
Claim 13
Dependent Claim
45 words
Apparatus according to claim 10, in which: the apparatus includes means for producing a coupling signal of amplitude representing the proximity of a casing coupling; and the coupling-indicative signal generating means produces a pulse having a width proportional to the intensity of the coupling signal.
Claim 14
Dependent Claim
59 words
Apparatus according to claim 10, in which the coupling-indicative pulse generating means comprises: charge storage means; current source means conneCted to charge the charge-storing means to a given value at a rate proportional to the current therefrom; and means for varying the value of the current from the current source means in accordance with proximity of a casing coupling.
Claim 15
Dependent Claim
30 words
Apparatus according to claim 12, in which the coupling-indicative means further comprises: means responsive to said sequential control means for rapidly conditioning the charge storing means to a reference value.
Claim 16
Dependent Claim
47 words
Apparatus according to claim 13, in which the coupling-indicative means further comprises: comparator means connected to the storage means for generating an output pulse having a duration proportional to the time period between the attainment of the reference and given values of charge by the storage means.
Claim 17
Dependent Claim
60 words
Apparatus according to claim 10, further comprising surface means including: means coupled to the cable conductor for developing a control signal in predetermined time reference to the arrival at the surface of the amplified electrical signal; and gating means responsive to the control signal for extracting a selected portion of the signals on the cable conductor including the coupling-indicative signal.
Claim 18
Dependent Claim
122 words
In a borehold logging system, apparatus for generating a signal representative of the proximity of a coupling between adjacent sections of a casing lining the borehole, comprising: charge-storing means; current source means connected to charge the charge-storing means to a given value at a rate proportional to the current therefrom; coupling detector means for varying the value of the current from the current source means in accordance with the proximity of a casing coupling; means for rapidly conditioning the charge storing means to a reference value; and comparator means connected to the storage means for generating an output pulse having a duration proportional to the time period between the attainment of the reference and given values of charge by the storage means.
Claim 19
Dependent Claim
122 words
In a borehold logging system, apparatus for generating a signal representative of the proximity of a coupling between adjacent sections of a casing lining the borehole, comprising: charge-storing means; current source means connected to charge the charge-storing means to a given value at a rate proportional to the current therefrom; coupling detector means for varying the value of the current from the current source means in accordance with the proximity of a casing coupling; means for rapidly conditioning the charge storing means to a reference value; and comparator means connected to the storage means for generating an output pulse having a duration proportional to the time period between the attainment of the reference and given values of charge by the storage means.
Claim 20
Dependent Claim
194 words
In apparatus for acoustically logging an earth borehole including a casing defining an annulus for a bonding material between earth formations and the casing to obtain indications concerning the bonding of the casing thereto, a downhole signal transmission system, comprising: a logging tool movable through the borehole, including at least one transmitter for sending acoustic energy through the borehole and casing and at least one receiver spaced from the transmitter for developing an electrical signal in response to each transmission of acoustic energy received thereby; a clock pulse generator for supplying a train of pulses; a sequence counter responsive to successive pulses from the clock pulse generator for providing a plurality of numerical control signals corresponding to respective numerical counts of the pulses in a given time interval; amplifying means coupled to the receiver for amplifying the electrical signals from the receiver; means operative with said amplifying means to provide at least two degrees of amplification thereby; and mode control means responsive to one of said numerical control signals for controlling said last-named means to provide at least two electrical signals amplified to different degrees during respective consecutive time intervals comprising a given sequence.
Claim 21
Dependent Claim
194 words
In apparatus for acoustically logging an earth borehole including a casing defining an annulus for a bonding material between earth formations and the casing to obtain indications concerning the bonding of the casing thereto, a downhole signal transmission system, comprising: a logging tool movable through the borehole, including at least one transmitter for sending acoustic energy through the borehole and casing and at least one receiver spaced from the transmitter for developing an electrical signal in response to each transmission of acoustic energy received thereby; a clock pulse generator for supplying a train of pulses; a sequence counter responsive to successive pulses from the clock pulse generator for providing a plurality of numerical control signals corresponding to respective numerical counts of the pulses in a given time interval; amplifying means coupled to the receiver for amplifying the electrical signals from the receiver; means operative with said amplifying means to provide at least two degrees of amplification thereby; and mode control means responsive to one of said numerical control signals for controlling said last-named means to provide at least two electrical signals amplified to different degrees during respective consecutive time intervals comprising a given sequence.
Claim 22
Dependent Claim
43 words
Apparatus as defined in claim 17, further comprising: a second receiver spaced from the first receiver, control means for selectively coupling a different one of the receivers to the amplifying means in each time interval and in a predetermined order during each sequence.
Claim 23
Dependent Claim
40 words
Apparatus as set forth in claim 18, further comprising: means responsive to at least one numerical control signal corresponding to a first given count of the counter during each time interval for generating a timing signal to energize the transmitter.
Claim 24
Dependent Claim
16 words
Apparatus according to claim 19, further comprising: means for coupling the timing signal to the conductor.
Claim 25
Dependent Claim
30 words
Apparatus in accordance with claim 20, in which: the timing signal means generates a narrow positive pulse portion and a narrow negative pulse portion, relative to a signal reference level.
Claim 26
Dependent Claim
46 words
Apparatus as defined in claim 19, further comprising: gating means responsive to at least one numerical control signal corresponding to a predetermined count of the counter greater than the first count for selecting at least a portion of a respective electrical signal during each time interval.
Claim 27
Dependent Claim
56 words
Apparatus as defined in claim 22, further comprising: means for generating a calibration signal of preselected amplitude and frequency, and calibration gating means responsive to a numerical control signal corresponding to a fourth count of the counter for connecting the calibration signal to the conductor in time displaced relation to the timing and selected electrical signals.
Claim 28
Dependent Claim
66 words
Apparatus in accordance with claim 22, in which the logging tool includes means for providing an electrical signal representative of radiation in the formations, the apparatus further comprising: means responsive to at least one numerical control signal corresponding to a distinct count of the counter for connecting the radiation signal to the conductor in time displaced relationship to the other connected signals during each time interval.
Claim 29
Dependent Claim
32 words
Apparatus according to claim 18, further comprising: means responsive to at least one numerical control signal for setting the counter to a predetermined initial count at the end of each time interval.
Claim 30
Dependent Claim
41 words
Apparatus according to claim 25, in which: the mode control means is responsive to the numerical control signal which sets the counter to the initial count to develop a unique set of electrical signals during each time interval of the sequence.
Claim 31
Dependent Claim
66 words
Apparatus according to claim 19, further including surface detection equipment comprising: detector means coupled to the cable conductor for developing a control signal having a predetermined time reference to said timing signal; and gating means responsive to the control signal and coupled to the conductor for extracting a selected portion of the signals on the conductor containing an amplified electrical signal from the downhole amplifying means.
Claim 32
Dependent Claim
72 words
Apparatus as defined in claim 27 in which the detector means includes: pulse detection means operable to develop a pulse output in response to a signal on the conductor preceding the arrival of the amplified electrical signal; and first and second delay means responsive to the pulse output of the detection means for generating respective first and second pulses comprising said control signal, said first and second pulses being displaced in time.
Claim 33
Dependent Claim
54 words
Apparatus according to claim 27, further comprising: radiation detector means carried by the logging tool and responsive to radiation emanating from the formations to provide signals representing such radiation; and means coupled to the sequence counter means for coupling such radiation signals to the cable conductor in response to a given numerical control signal.
Claim 34
Dependent Claim
48 words
Apparatus according to claim 29, further comprising: second gating means at the surface responsive to the first gating means for separating from the cable signals the radiation signals, the second gating means being operative in time referenced relation to the arrival at the surface of said timing signal.
Claim 35
Dependent Claim
178 words
A logging tool for acoustically logging a borehole comprising: at least one transmitting means for sending acoustic energy into the media proximate to the transmitting means; first acoustic receiving means spaced from said transmitting means and adapted for developing a first electrical signal in response to selected transmissions of acoustic energy received thereby; second acoustic receiving means spaced from said transmitting means and said first acoustic receiving means and adapted for developing a second electrical signal in response to selected transmissions of acoustic energy received thereby; means for detecting radiation emanating from media proximate to said logging tool and providing third electrical signals representative of the detected radiation; means for repetitively actuating said transmitting means at preselected time intervals and generating a fourth electrical signal representative of the time of actuation thereof; means for sequentially processing said first, second and fourth electrical signals and said first, third and fourth electrical signals during alternate ones of said preselected time intervals; and local timing means in said logging tool for controlling, respectively said actuating means and said sequential processing means.
Claim 36
Dependent Claim
178 words
A logging tool for acoustically logging a borehole comprising: at least one transmitting means for sending acoustic energy into the media proximate to the transmitting means; first acoustic receiving means spaced from said transmitting means and adapted for developing a first electrical signal in response to selected transmissions of acoustic energy received thereby; second acoustic receiving means spaced from said transmitting means and said first acoustic receiving means and adapted for developing a second electrical signal in response to selected transmissions of acoustic energy received thereby; means for detecting radiation emanating from media proximate to said logging tool and providing third electrical signals representative of the detected radiation; means for repetitively actuating said transmitting means at preselected time intervals and generating a fourth electrical signal representative of the time of actuation thereof; means for sequentially processing said first, second and fourth electrical signals and said first, third and fourth electrical signals during alternate ones of said preselected time intervals; and local timing means in said logging tool for controlling, respectively said actuating means and said sequential processing means.
Claim 37
Dependent Claim
54 words
Apparatus according to claim 31, further including: means for generating a fifth electrical signal adapted to enable the identification of the alternate ones of said preselected time intervals during which said first, second and fourth electrical signals are sequentially processed from those during which said first, third and fourth electrical signals are sequentially processed.
Claim 38
Dependent Claim
159 words
Borehole logging apparatus, comprising: a logging tool movable through the borehole and including mutually spaced energy transmitting means and receiving means for emitting and detecting energy, respectively; means for repetitively energizing the transmitting means at preselected intervals to effect corresponding emissions of energy and thereby to develop by the receiving means for each thereof an electrical signal representative of energy received; signal processing means synchronized with the emissions of energy for varying in a predetermined manner that is different for successive time intervals in a predetermined sequence of time intervals the electrical characteristics of said electrical signals; and sequence control means in the tool developing control signals for establishing in the processing means a signal processing sub sequence for each successive time interval in said predetermined sequence of time intervals, each such processing sub sequence comprising plural time intervals, and each such sub sequence effecting a repetitive set of electrical signal characteristic varying operations by the signal process-ing means.
Claim 39
Dependent Claim
159 words
Borehole logging apparatus, comprising: a logging tool movable through the borehole and including mutually spaced energy transmitting means and receiving means for emitting and detecting energy, respectively; means for repetitively energizing the transmitting means at preselected intervals to effect corresponding emissions of energy and thereby to develop by the receiving means for each thereof an electrical signal representative of energy received; signal processing means synchronized with the emissions of energy for varying in a predetermined manner that is different for successive time intervals in a predetermined sequence of time intervals the electrical characteristics of said electrical signals; and sequence control means in the tool developing control signals for establishing in the processing means a signal processing sub sequence for each successive time interval in said predetermined sequence of time intervals, each such processing sub sequence comprising plural time intervals, and each such sub sequence effecting a repetitive set of electrical signal characteristic varying operations by the signal process-ing means.
Claim 40
Dependent Claim
186 words
Borehole logging apparatus, comprising: a logging tool movable through the borehole and including mutually spaced energy transmitting means and receiving means for emitting and detecting energy, respectively; means for repetitively energizing the transmitting means at preselected intervals to effect corresponding emissions of energy and thereby to develop by the receiving means for each thereof an electrical signal representative of energy received; signal processing means synchronized with the emissions of energy for varying in a predetermined manner that is different for different time intervals in a predetermined sequence the electrical characteristics of said electrical signals; sequence control means in the tool developing control signals for establishing in the processing means a signal processing sequence comprised of plural time intervals, each sequence effecting a repetitive set of electrical signal characteristic varying operations by the signal processing means; means synchronized with the repetitive energizing means for generating an identification signal that is distinct from said electrical signal and different for at least consecutive intervals of said sequence; an electrical output cable for the tool; and means for coupling the identifying and electrical signals to the output cable in sequence.
Claim 41
Dependent Claim
186 words
Borehole logging apparatus, comprising: a logging tool movable through the borehole and including mutually spaced energy transmitting means and receiving means for emitting and detecting energy, respectively; means for repetitively energizing the transmitting means at preselected intervals to effect corresponding emissions of energy and thereby to develop by the receiving means for each thereof an electrical signal representative of energy received; signal processing means synchronized with the emissions of energy for varying in a predetermined manner that is different for different time intervals in a predetermined sequence the electrical characteristics of said electrical signals; sequence control means in the tool developing control signals for establishing in the processing means a signal processing sequence comprised of plural time intervals, each sequence effecting a repetitive set of electrical signal characteristic varying operations by the signal processing means; means synchronized with the repetitive energizing means for generating an identification signal that is distinct from said electrical signal and different for at least consecutive intervals of said sequence; an electrical output cable for the tool; and means for coupling the identifying and electrical signals to the output cable in sequence.
Claim 42
Dependent Claim
106 words
In a borehole logging apparatus, the combination of: a logging tool movable through the borehole including means for developing plural logging signals and an electrical identification signal preceding the plural logging signals and having electrical characteristics differing from the characteristics of the logging signals thereby to be distInguishable therefrom; an output conductor for conveying the identification and plural logging signals to the surface; and surface signal processing means including (a) at least two signal channels for carrying the respective plural logging signals, and (b) means responsive to the identification signal for sequentially directing individual ones of the plural signals to separate ones of the signal channels.
Claim 43
Dependent Claim
106 words
In a borehole logging apparatus, the combination of: a logging tool movable through the borehole including means for developing plural logging signals and an electrical identification signal preceding the plural logging signals and having electrical characteristics differing from the characteristics of the logging signals thereby to be distInguishable therefrom; an output conductor for conveying the identification and plural logging signals to the surface; and surface signal processing means including (a) at least two signal channels for carrying the respective plural logging signals, and (b) means responsive to the identification signal for sequentially directing individual ones of the plural signals to separate ones of the signal channels.
Claim 44
Dependent Claim
56 words
Apparatus as defined in claim 35, in which the logging signal directing means includes: first and second controllable signal gating means each receiving the plural logging signals connected respectively to a different one of the signal channels; and gate control means for sequentially activating the first and second gating means in response to the identification signal.
Claim 45
Dependent Claim
54 words
Apparatus as set forth in claim 36, in which: the gate control means includes means for detecting the arrival at the surface of the identification signal to produce at least one signal operable to activate the first gating means and thereby pass one of the plural logging signals to one of the signal channels.
Claim 46
Dependent Claim
40 words
Apparatus according to claim 37, further comprising: first delay means interposed between the identification signal detecting means and the first gating means to delay activation of said gating means until a specified time period following arrival of the identification signal.
Claim 47
Dependent Claim
43 words
Apparatus according to claim 37, in which the gate control means further includes: delay means responsive to said one signal for producing a gate control signal operable to deactivate the first gating means a preselected time period following arrival of the identification signal.
Claim 48
Dependent Claim
29 words
Apparatus according to claim 39, in which: the second gating means is responsive to the gate control signal to be activated thereby following deactivation of the first gating means.
Claim 49
Dependent Claim
26 words
Apparatus as defined in claim 40, in which: the second gating means is activated for a predetermined time period in response to the gate control signal.
Claim 50
Dependent Claim
31 words
Apparatus as set for in claim 41, further comprising: means responsive to the gate control signal for generating a pulse having said predetermined period, the second gating means receiving said pulse.
Claim 51
Dependent Claim
82 words
Apparatus according to claim 36, further comprising: means in said first signal channel for storing an electrical signal in response to and representing the logging signal passing to said channel upon activation of the first gating means; a first channel output conductor; and means interconnected between said channel output conductor and the storing means and responsive to the gate control signal for transferring to said channel output conductor said electrical signal in timed relation to the occurrence of the gate control signal.
Claim 52
Dependent Claim
145 words
A logging tool for acoustically logging a cased borehole and including: at least one transmitter and spaced apart receiver means for developing first and second electrical signals representative of the emission and detection of acoustic energy; variable gain amplifying means for providing different gain amplification; means for selectively coupling one of said receiver means to said gain amplifying means; means for repetitively actuating said transmitter; means for detecting radiation emanating in a borehole and providing third electrical signals representative of the detected radiation; means for detecting couplings in a well casing and providing fourth electrical signals representative of the detection of such couplings; and means for sequentially processing said first, second, third and fourth signals for transmission during each time interval, including means for operating said selectively coupling means to couple one of said receiver means to said gain amplifying means during each time interval.
Claim 53
Dependent Claim
145 words
A logging tool for acoustically logging a cased borehole and including: at least one transmitter and spaced apart receiver means for developing first and second electrical signals representative of the emission and detection of acoustic energy; variable gain amplifying means for providing different gain amplification; means for selectively coupling one of said receiver means to said gain amplifying means; means for repetitively actuating said transmitter; means for detecting radiation emanating in a borehole and providing third electrical signals representative of the detected radiation; means for detecting couplings in a well casing and providing fourth electrical signals representative of the detection of such couplings; and means for sequentially processing said first, second, third and fourth signals for transmission during each time interval, including means for operating said selectively coupling means to couple one of said receiver means to said gain amplifying means during each time interval.
Claim 54
Dependent Claim
110 words
A logging tool for acoustically logging a cased borehole and including: means for emitting and detecting acoustic energy in a borehole and for developing first and second electrical signals representative of the emission and detection of acoustic energy; means for repetitively actuating said emitting means at preselected time intervals; means for detecting radiation emanating in a borehole and providing third electrical signals representative of the detected radiation; means for detecting couplings in a well casing and providing fourth electrical signals representative of the detection of such couplings; calibrating means for providing calibration signals; and means for sequentially processing said first, second, third, fourth and calibrating signals during each time interval.
Claim 55
Dependent Claim
110 words
A logging tool for acoustically logging a cased borehole and including: means for emitting and detecting acoustic energy in a borehole and for developing first and second electrical signals representative of the emission and detection of acoustic energy; means for repetitively actuating said emitting means at preselected time intervals; means for detecting radiation emanating in a borehole and providing third electrical signals representative of the detected radiation; means for detecting couplings in a well casing and providing fourth electrical signals representative of the detection of such couplings; calibrating means for providing calibration signals; and means for sequentially processing said first, second, third, fourth and calibrating signals during each time interval.
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) | 1976-07-30 | 1977-01-29 | 1977-07-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-30 | 1981-01-29 | 1981-07-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-30 | 1985-01-29 | 1985-07-31 | $7700.00 | Window Closed / Lapsed |