Method and apparatus for detecting digital carrier signals on telephone cables

A method of distinguishing between first and second electrical signals carried by a pair of conductors, said first signals being carried by said conductor pair, and said second signals being electrically coupled to said conductor pair, comprising the steps of:

• a) inserting capacitive probe means for collecting an electrical signal between the conductors of said pair;
• b) collecting a portion of a signal on said conductor pair with said capacitive probe means;
• c) providing said collected signal to differential inputs of an amplifier means;
• d) producing an output from said amplifier means, and determining from said output whether said collected signal is one of said first signals or one of said second signals.

A method of distinguishing between a valid signal and a crosstalk signal on a pair of conductors, comprising the steps of:

• a) providing a capacitive probe made up of a pair of conductive plates that are separated from each other;
• b) connecting said probe plates to inputs of a balanced amplifier;
• c) inserting said probe between the conductors of said pair;
• d) collecting a portion of said signal from said pair with said probe;
• e) producing an output from said amplifier of said collected signal, and determining from said output whether a valid signal or a crosstalk signal is on said pair, wherein a valid signal produces a stronger output than a crosstalk signal.