Subscriber Line Interface Circuit Signal Conversion Isolation
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Solution Overview
Problem
Conventional subscriber line interface circuits are costly due to numerous high-voltage and high-power components, and they are susceptible to variations in tip and ring line signals, requiring additional circuitry and power for signal processing.
Innovation Solution
A subscriber line interface circuit apparatus that includes a linefeed circuit with a unique signal conversion circuit providing differential and common mode signals, allowing the subscriber line control circuit to be isolated from the tip and ring signals, thereby reducing the need for signal processing and increasing independence from signal instabilities, and enabling remote fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional subscriber line interface circuits use numerous high-voltage and high-power components, then the circuit can handle analog functions and drive telephone lines, but the cost increases and the circuit becomes susceptible to signal variations
Solution Approach 1:
The patent introduces a signal conversion circuit as an intermediary between the tip/ring signal lines and the subscriber line control circuit. This conversion circuit transforms the analog tip and ring signals into differential mode signals, which are then processed by the SLCC. This intermediary conversion isolates the control circuit from direct exposure to signal variations on the tip and ring lines, improving reliability while reducing the need for complex signal processing in the control circuit.
2Productivity
If the subscriber line control circuit directly processes tip and ring signals, then signal processing can be performed, but additional circuitry and power are required
Solution Approach 1:
The patent changes the parameter domain of the signals by converting analog tip and ring signals into differential mode signals. This parameter transformation allows the subscriber line control circuit to operate in a different signal domain that is more suitable for digital processing, improving signal processing efficiency while reducing power consumption requirements for the control circuit.
3Reliability
If the subscriber line control circuit is isolated from tip and ring signals, then independence from signal instabilities is achieved, but the circuit requires signal conversion
Solution Approach 1:
The signal conversion circuit serves as an intermediary that provides isolation between the tip/ring signal lines and the subscriber line control circuit. By converting signals before they reach the control circuit, this intermediary component enables the control circuit to operate independently from signal instabilities on the telephone lines, improving reliability while the added conversion circuitry remains relatively simple in design.
Data Source
AI summary
A subscriber line interface circuit apparatus includes a linefeed circuit and a subscriber line control circuit (SLCC). In an embodiment, the linefeed circuit includes a signal conversion circuit which provides a differential mode signal and a common mode signal in response to at least a tip signal and a ring signal from the subscriber loop. The linefeed circuit includes a tip control circuit and a ring control circuit. In an embodiment, the SLCC is provided in a single integrated circuit chip and is coupled to the linefeed circuit which isolates the SLCC from the tip or ring signals. The SLCC includes a first and a second differential mode inputs for receiving the differential mode signal, and a common-mode input for receiving the common-mode signal. In an embodiment, the SLCC also provides various tip control signals and ring control signals to the tip control circuit and the ring control circuit, respectively.