Performance monitoring for loops

Apparatus for coupling to a communication channel in which information is encoded as a pulse stream of alternate mark inversion bipolar pulses comprising:

• a) a code violation circuit for determining the occurrence of an unintentional bipolar sequence violation as distinguished from an intentional bipolar sequence violation wherein an intentional bipolar violation is signalled by an XOV bipolar violation sequence in which a violation pulse V having the same polarity as a previous pulse is inserted into the pulse stream and is preceded by insertion of an X pulse two pulses prior to the V pulse which may have a polarity or no polarity such that successive violation pulses alternate in polarity and insertion of a zero value pulse between the X and V pulses;
• and
• b) disabling means for disabling the communication channel when the rate of occurrence of said unintentional violations exceeds a predetermined number.

A loop performance monitor for detecting the occurrence of unintentional bipolar violations in which digital signals are encoded as alternate-mark-inversion bipolar pulses and transmitted on each of two rails of a transmit loop wherein one rail is a positive rail and the other is a negative rail which carries the inverse of the pulses on the other rail and wherein a bipolar violation occurs when a present pulse on one rail has the same polarity as a previous pulse on the same rail, and wherein intentional bipolar violations are indicated by an XOV series of pulses, said monitor comprising:

• a) a first circuit for receiving the present pulses and outputting the present pulses from one rail;
• b) a second circuit for storing the present pulses and outputting the present pulses delayed by one pulse interval, such that the outputs of the second circuit are the previous pulses;
• c) a third circuit for determining the presence of pulses from the first and second circuit of the same polarity and indicating a bipolar violation upon such occurrence in the event an XOV series of pulses is not present.

A method of communication in which information is transmitted as a stream of digital bits comprising the steps of:

• a) determining the occurrence of loop code violations, wherein a loop code violation comprises the occurrence of an unintentional bipolar violation as distinguished from an intentional bipolar violations and wherein an intentional bipolar violation is signalled by an XOV bipolar violation sequence in which a violation bit V, having the same polarity as a previous bit, is intentionally inserted into the bit stream preceded by intentional insertion of an X bit two bits prior to the violation which may comprise a bit having a polarity or not polarity such that successive violations alternate in polarity and intentional insertion of a zero value bit between the X and V bits;
• and
• b) disabling the communication when the frequency of occurrence of loop code violations exceeds a predetermined rate.

A method of communication in which information is encoded as a pulse stream of alternate mark inversion bipolar pulses comprising the steps of:

• a) determining the occurrence of an unintentional bipolar sequence violation as distinguished from an international bipolar sequence violation, wherein an intentional bipolar violation is signalled by an XOV bipolar violation sequence in which a violation pulse V having the same polarity as a previous pulse is inserted into the pulse stream and is preceded by insertion of an X pulse two pulses prior to the V pulse which may have a polarity or no polarity such that successive violation pulses alternate in polarity and intentional insertion of a zero value pulse between the X and V pulses;
• and
• b) disabling communication when the rate of said unintentional violations exceeds a predetermined number.