Lead line supervision system

A method for detecting malfunction conditions in an automatic meter reading system including a meter with output switching means having first and second output terminals and current gating means coupled therebetween, said output switching means periodically closing for providing a plurality of meter pulses, a data receiving station, and a pair of lead lines coupling said first and second terminals of said meter and said data receiving station, comprising:

• applying a potential of a first polarity to said data receiving station;
• generating data pulses of said first polarity upon periodic closures of said output switching means;
• detecting the presence of said data pulses of said first polarity for a first preselected duration;
• providing a first output signal when the presence of one of said data pulses exceeds said first preselected duration;
• supplying a detection signal of a second polarity to said data transmitting station for a second preselected duration;
• detecting the presence or absence of said detection signal for said second preselected duration from said data receiving station;
• and
• providing a second output signal when the absence of said detection signal exceeds said second preselected duration.

A lead line supervision circuit for detecting malfunction conditions in a data transmission system including a data transmitting station and a data receiving station connected over first and second lead lines, said data transmitting station including output switching means having a first terminal coupled with said first lead line and a second output terminal coupled with said second lead line and operable with said data receiving station to provide data pulses thereto, and output current gating means coupled between said first and second lead lines, said lead line supervision circuit comprising:

• means for applying a potential of a first polarity to said data transmitting station;
• means for generating data pulses of said first polarity upon periodic closures of said switching means;
• means for detecting the presence of each of said data pulses of said first polarity continuing for a first preselected duration;
• and
• means for providing a first output signal when the presence of said data pulses of said first polarity exceeds said first preselected duration.

A circuit for detecting malfunction conditions in a data transmission system for passing data between a data transmitting station and a data receiving station over first and second data transmission lines, said data transmitting station having current gating means coupling said first and second data transmission lines, said malfunction detection circuit comprising:

• first signal generating means for providing data pulses of a first polarity;
• first sensing means for sensing the presence of said first data pulses for at least a first predetermined duration and providing a first sensing signal when said data signal exceeds said first predetermined duration;
• output circuit means for receiving said first sensing signal and providing an output signal indicative of a malfunction;
• second detection signal generating means for providing a second detection signal of a second polarity for at least a second predetermined duration;
• second sensing means for sensing the presence or the absence of said second detection signal for at least said second predetermined duration and providing a second sensing signal when the absence of said detection signal exceeds said second preselected duration;
• and
• output circuit means for receiving said second sensing signal and providing an output signal indicative of the absence of said second sensing signal.

A lead line supervision circuit incorporated in a meter reading system having an automatic meter reader coupled with a data receiving station via first and second data lines, said automatic meter reader including output switching means having a first terminal coupled with said first data line and a second terminal coupled with said second data line, said output switching means periodically closing upon detection of use of a utility, and current gating means coupled with said first and second switching terminals, said supervision circuit comprising:

• first and second data ports coupled with said first and second data lines, respectively, said data ports operable in a first mode for providing data pulses of a first polarity when said output switching means is closed;
• pulse sequencer means for providing an enable signal to said first and second data ports for operating said data ports in a second mode for providing an open circuit test signal of a second polarity to said data lines;
• and
• pulse detecting circuit means for detecting said data pulses of said first polarity and continuing for a first preselected duration and providing a first malfunction signal indicative of a short circuit condition and for detecting said open circuit test signal and providing a second malfunction signal indicative of an open circuit condition.