Line current protection circuit for use with a PCMCIA-architecture modem card
DCFirst Claim
1. A protection circuit intended for use with a line interface circuit that is electrically connectable to a telephone line, the protection circuit comprising:
- relay means, connected between the interface circuit and the telephone line, for selectively providing an open or a closed connection between the line interface circuit and the telephone line; and
detection means for detecting the magnitude of a line-current presented to the interface circuit via a supply voltage placed across the telephone line and for causing the relay means to be opened or closed depending on the magnitude of the line-current.
11 Assignments
Litigations
0 Petitions
Accused Products
Abstract
A novel line-current protection circuit that is useable with a PCMCIA modem card is disclosed. The protection circuit is adapted to detect when an excessive voltage is present across the tip and the ring leads of a telephone subscriber loop by sensing the amount of line-current being supplied to line interface circuitry disposed on the PCMCIA modem card. The protection circuit includes a current sensing circuit portion that is placed in series with the tip lead and which detects when the line current exceeds a predetermined maximum amount. In the event the line current exceeds the maximum amount, the current sensing circuit asserts an excessive line current signal which is being monitored by a digital processor. The digital processor responds by causing a relay circuit to be opened, thereby causing the PCMCIA modem to be in an "on-hook" state. When the magnitude of the line-current does not exceed the predetermined maximum amount, the excessive line current signal is not asserted and the digital processor responds by closing the relay circuitry, thereby causing the PCMCIA modem to be in a "off-hook" state. The protection circuit also includes a backup fuse, which will trip if the primary components of the protection circuit fail.
51 Citations
23 Claims
-
1. A protection circuit intended for use with a line interface circuit that is electrically connectable to a telephone line, the protection circuit comprising:
-
relay means, connected between the interface circuit and the telephone line, for selectively providing an open or a closed connection between the line interface circuit and the telephone line; and detection means for detecting the magnitude of a line-current presented to the interface circuit via a supply voltage placed across the telephone line and for causing the relay means to be opened or closed depending on the magnitude of the line-current. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A protection circuit intended for use with a line interface circuit that is electrically connectable to a telephone line, the protection circuit comprising:
-
relay means, connected between the line interface circuit and the telephone line, for selectively providing an open or a closed connection between the line interface circuit and the telephone line; current sensing means for providing an excessive line current signal when a line-current presented to the interface circuit via a supply voltage placed across the telephone line exceeds a predetermined magnitude; and controller means, responsive to the excessive line current signal, for controlling the relay means. - View Dependent Claims (8, 9, 10, 11)
-
-
12. A protection circuit intended for use in a PCMCIA modem card having a telephone line interface circuit that is electrically connectable between the ring lead and tip lead of an external telephone subscriber line connector, the protection circuit comprising:
-
relay means, connected in series in the tip lead of the telephone line between the line interface circuit and the external telephone line connector, for selectively providing an open or a closed connection between the line interface circuit and the tip and the ring leads of the external telephone line connector; current sensing means for providing an excessive line current signal when a line-current presented to the line interface circuit via a supply voltage placed across the tip lead and the ring lead of the telephone line exceeds a predetermined magnitude; and controller means, responsive to the excessive line current signal, for controlling the relay means, whereby the relay means opens or closes the connection depending on the status of the excessive line current signal. - View Dependent Claims (13, 14, 15, 16, 17, 18)
-
-
19. A PCMCIA modem card having a telephone line interface circuit that is electrically connectable between the ring lead and tip lead of an external telephone subscriber line connector, and a protection circuit, the protection circuit comprising:
-
a solid-state relay device connected in series with the tip lead between the external telephone line connector and the line interface circuit, the relay device being selectively operable to be either in a closed or opened arrangement; a sensing resistor connected in series with the tip lead between the external telephone line connector and the line interface circuit such that any line-current flowing through the tip lead to the interface circuit resulting from a supply voltage placed across the tip lead and the ring lead flows through the sensing resistor; an optoelectronic device connected in parallel with the sensing resistor such that the optoelectronic device responds to the line-current flowing through the sensing resistor by providing an excessive line current signal when the line-current exceeds a predetermined magnitude; a digital processor, the digital processor being electrically connected to both the optoelectronic device and the relay device, whereby the digital processor programmably causes the relay device to be either opened or closed depending upon the status of said excess line current signal. - View Dependent Claims (20, 21)
-
-
22. A protection circuit intended for use in a PCMCIA modem card having a telephone line interface circuit that is electrically connectable between the ring lead and tip lead of an external telephone subscriber line connector, the protection circuit comprising:
-
relay means, connected in series in the ring lead of the telephone line between the line interface circuit and the external telephone line connector, for selectively providing an open or a closed connection between the line interface circuit and the tip and the ring leads of the external telephone line connector; current sensing means for providing an excessive line current signal when a line-current presented to the line interface circuit via a supply voltage placed across the ring lead and the tip lead of the telephone line exceeds a predetermined magnitude; and controller means, responsive to the excessive line current signal, for controlling the relay means, whereby the relay means opens or closes the connection depending on the status of the excessive line current signal.
-
-
23. A PCMCIA modem card having a telephone line interface circuit that is electrically connectable between the ring lead and tip lead of an external telephone subscriber line connector, and a protection circuit, the protection circuit comprising:
-
a solid-state relay device connected in series with the ring lead between the external telephone line connector and the line interface circuit, the relay device being selectively operable to be either in a closed or opened arrangement; a sensing resistor connected in series with the ring lead between the external telephone line connector and the line interface circuit such that any line-current flowing through the tip lead to the interface circuit resulting from a supply voltage placed across the tip lead and the ring lead flows through the sensing resistor; an optoelectronic device connected in parallel with the sensing resistor such that the optoelectronic device responds to the line-current flowing through the sensing resistor by providing an excessive line current signal when the line-current exceeds a predetermined magnitude; a digital processor, the digital processor being electrically connected to both the optoelectronic device and the relay device, whereby the digital processor programmably causes the relay device to be either opened or closed depending upon the status of said excess line current signal.
-
Specification