Circuit for detecting current variations

摘要

The circuit of the present invention detects variations of a current IL flowing in a telephone line LL. A low-value resistor r is connected in series with line LL. A constant voltage generator is connected across this resistor. The current Is applied to resistor r by the contant voltage generator varies as a function of IL. This being so, a measurement of the variations of Is will reflect variations of IL and, therefore, can be used to detect both amplitude and directional variations of IL.