EP0097314A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Telephone line interface circuit
Assignee: Applied Spectrum Technologies Inc
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Filing: 1983-06-14
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Granted: —
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Expires: 2003-06-14
Abstract
Abstract A circuit for coupling digital or analog data signals to a telephone line. A direct coupled transistorized circuit is disclosed having three different impedance conditions: on-hook, off-hook, and loop-test. Consequently, data can be transmitted regardless of the on-hook or off-hook status of the associated telephone sets and regardless of whether or not the telephone sets are in use. In addition, data transmission can range over a frequency spectrum of approximately d-c to frequencies in the data-over-voice range. Because of the variable bridging impedance, the drive impedance is not too low during on-hook ringing and the circuit need not be disconnected during ringing or testing.
Inventors
- 👤 Donald W. Moses
- 👤 Charles Hustig
- 👤 Ray C. Ballard
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 16:04
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/06; H04M11/066; H04M11/062
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
91 words
A communications medium interface circuit which couples data to a telephone line during all normal operating conditions of the line comprising: a first transistorized output stage (20) having a low bridging impedance operative when telephones connected to the telephone line are off-hook; a second transistorized output stage (21) having a high bridging impedance operative when telephones connected to the telephone line are on-hook; and means for switching (D43, Q4) the circuit between the first output stage (20) and the second output stage (21) depending upon the condition of the telephone line.
Claim 2
Dependent Claim
91 words
A communications medium interface circuit which couples data to a telephone line during all normal operating conditions of the line comprising: a first transistorized output stage (20) having a low bridging impedance operative when telephones connected to the telephone line are off-hook; a second transistorized output stage (21) having a high bridging impedance operative when telephones connected to the telephone line are on-hook; and means for switching (D43, Q4) the circuit between the first output stage (20) and the second output stage (21) depending upon the condition of the telephone line.
Claim 3
Dependent Claim
59 words
The communications medium interface circuit of claim 1, wherein data is coupled to the telephone line through the first output stage (20) when one or more telephones connected to the telephone line are off-hook and wherein data is coupled to the telephone line through the second output stage (21) when all telephones connected to the telephone line are on-hook.
Claim 4
Dependent Claim
72 words
The communications medium interface circuit of claim 1 further comprising: means for detecting (D45) when a test voltage is applied to the telephone line; and means ( Q 1) for turning off the first output stage transistor (Q3) and the second output stage transistor (Q2) when a test voltage is applied to the telephone line so that the bridging impedance of the circuit is very high when the line is being tested.
Claim 5
Dependent Claim
34 words
The communications medium interface circuit of claim 1, wherein the bridging impedance of the first transistor output stage (20) is approximately two kilohms when one or more telephones connected to the line are off-hook.
Claim 6
Dependent Claim
33 words
The communications medium interface circuit of claim 1, wherein the bridging impedance of the second output stage (21) is greater than one hundred kilohms when telephones connected to the telephone lines are on-hook.
Claim 7
Dependent Claim
31 words
The communications medium interface circuit of claim 1, wherein the bridging impedance of the circuit is greater than a hundred kilohms when a test voltage is applied to the telephone line.
Claim 8
Dependent Claim
16 words
The communications medium interface circuit of claim'1, wherein the output of the first transistorized output stage
Claim 9
Dependent Claim
119 words
In United States Patent No. 4,224,478 a microprocessor controlled coupling circuit is disclosed. The microprocessor periodically pulses the circuit to determine whether or not an associated telephone set is off-hook. When off-hook, data cannot be transmitted. When on-hook the microprocessor is enabled to transmit or receive data, again, coupled to the telephone line with an isolation transformer in series with at least one d-c blocking capacitor. .. Consequently, the coupling circuits of both of these inventions enable the transmission of frequency data in a limited frequency range and then only in one operating condition of the telephone line. These prior coupling circuits are voltage mode devices. Data signals transmitted are superimposed onto whatever d-c voltage is on the line.
Claim 10
Dependent Claim
119 words
In United States Patent No. 4,224,478 a microprocessor controlled coupling circuit is disclosed. The microprocessor periodically pulses the circuit to determine whether or not an associated telephone set is off-hook. When off-hook, data cannot be transmitted. When on-hook the microprocessor is enabled to transmit or receive data, again, coupled to the telephone line with an isolation transformer in series with at least one d-c blocking capacitor. .. Consequently, the coupling circuits of both of these inventions enable the transmission of frequency data in a limited frequency range and then only in one operating condition of the telephone line. These prior coupling circuits are voltage mode devices. Data signals transmitted are superimposed onto whatever d-c voltage is on the line.
Claim 11
Dependent Claim
4 words
SUMMARY OF THE INVENTION
Claim 12
Dependent Claim
4 words
SUMMARY OF THE INVENTION
Claim 13
Dependent Claim
61 words
The current invention is a unique, inexpensive circuit design which enables the continuous transmission of data over the telephone line whether or not the associated telephone sets are on-hook, off-hook, in use or during ringing and testing. It remains connected to the line at all times and does not require any additional microprocessor or modem control device during or for operation.
Claim 14
Dependent Claim
61 words
The current invention is a unique, inexpensive circuit design which enables the continuous transmission of data over the telephone line whether or not the associated telephone sets are on-hook, off-hook, in use or during ringing and testing. It remains connected to the line at all times and does not require any additional microprocessor or modem control device during or for operation.
Claim 15
Dependent Claim
26 words
The circuit of the present invention has three bridging impedance conditions; when the telephone is on-hook, when the telephone is off-hook, and during the loop-test condition.
Claim 16
Dependent Claim
26 words
The circuit of the present invention has three bridging impedance conditions; when the telephone is on-hook, when the telephone is off-hook, and during the loop-test condition.
Claim 17
Dependent Claim
43 words
The circuit operates to vary the loop current in the line. Therefore, whatever current is flowing, whether it is zero current during the on-hook condition or approximately twenty milliamps during the off-hook condition, the circuit adds to that current flow an incremental amount.
Claim 18
Dependent Claim
43 words
The circuit operates to vary the loop current in the line. Therefore, whatever current is flowing, whether it is zero current during the on-hook condition or approximately twenty milliamps during the off-hook condition, the circuit adds to that current flow an incremental amount.
Claim 19
Dependent Claim
79 words
The circuit of the present invention also has three basic operating states. When the telephone is on-hook a first transistor becomes the output driver. ) Because of the circuit configuration associated with the first output driver an average on-hook. current sink of approximately 0.5 milliamp with a 0.25 milliamp peak-to-peak a-c signal results, yielding an average bridging impedance of over one hundred kilohms. This is ) too high an impedance to interfere with normal ringing operation and the like.
Claim 20
Dependent Claim
79 words
The circuit of the present invention also has three basic operating states. When the telephone is on-hook a first transistor becomes the output driver. ) Because of the circuit configuration associated with the first output driver an average on-hook. current sink of approximately 0.5 milliamp with a 0.25 milliamp peak-to-peak a-c signal results, yielding an average bridging impedance of over one hundred kilohms. This is ) too high an impedance to interfere with normal ringing operation and the like.
Claim 21
Dependent Claim
45 words
During the off-hook condition a second transistor becomes the output driver. The circuit configuration associated with the second output driver results in a total average sink current of 2.7 milliamps. This causes an average bridging impedance during the off-hook condition of less than two kilohms.
Claim 22
Dependent Claim
45 words
During the off-hook condition a second transistor becomes the output driver. The circuit configuration associated with the second output driver results in a total average sink current of 2.7 milliamps. This causes an average bridging impedance during the off-hook condition of less than two kilohms.
Claim 23
Dependent Claim
28 words
During the loop-test condition a third transistor causes the driver transistors to be turned off. The bridging impedance in this condition is then greater than two hundred kilohms.
Claim 24
Dependent Claim
28 words
During the loop-test condition a third transistor causes the driver transistors to be turned off. The bridging impedance in this condition is then greater than two hundred kilohms.
Claim 25
Dependent Claim
66 words
The resulting transistorized circuit is a circuit which stays across the line under all operating conditions. It functions to transmit data on the telephone line during either the on-hook or off-hook condition, when the telephone is in use and when it is 14. The communications medium interface circuit of claim 12, wherein the filtering means (C52, C55, C56) has a cut-off frequency of approximately three kilohertz.
Claim 26
Dependent Claim
48 words
The communications medium interface circuit of claim 1 further comprising: means for generating noise (90) connected to the first output stage (20) so that a low white background noise is generated on the line when one or more of the telephones connected to the telephone line are off-hook.
References Cited (Backward Citations)
No citation records indexed.
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