Test circuit automatically measuring crosstalk between telephones - by switching various capacitors into bridge and having output coupled to comparator

摘要

The test circuit, for automatically measuring crosstalk between telephone circuits incorporating cables, has a bridge coupled to the circuit being tested and with its balance state indicated. A bank of capacitors (8) is connected in parallel with the balancing arm of the bridge (1). The bank contains capacitors that can be switched in parallel with one another to give a total capacitance covering all values in a given range. A rectifier (5) is connected into the bridge and its output is coupled to a comparator (6) connected to the input of a register (7). The register controls the switching on of the capacitors, and is in the form of a successive approximation register.