Telephone line tester

A circuit for testing a telephone line to provide an indication of whether the line is open or shorted, has the correct line voltage thereon, and is of the correct polarity said circuit comprising:

• switch means connected to a telephone line for connecting said telephone line between a first portion of said circuit and a second portion of said circuit the first portion of said circuit testing said telephone line for polarity and the second portion of said circuit testing said telephone line for line voltage;
• open or shorted conditions, the first portion of said circuit including first and second opposite polarity LED's connected across the selected telephone line one or the other of said LED's illuminating providing an indication of the polarity of the signal on said telephone line;
• first and second comparators connected across said selected telephone line for comparing the signal on said telephone line with high and low reference signals and for generating an output indication of the signal on said telephone lines exceeds said high or low reference signals;
• a third comparator connected to the output of said first and second comparators and to said high reference signal for generating an output signal to indicate that the signal on said telephone line is within said high and low reference signals;
• and said second portion of said circuit including a fourth comparator having a first input and a second input, means for generating a threshold voltage connected to said second input;
• said fourth comparator generating an output signal if the signal on said telephone line exceeds said threshold.

A circuit for testing the telephone line comprising:

• means to monitor the AC voltage on the telephone line;
• first comparator means connected to said monitoring means;
• a source of reference voltage connected to said comparator means;
• said comparator means generating a first output indication if said AC voltage exceeds said reference voltage thereby indicating a ground fault;
• first and second opposite polarity indicators connected across said telephone line to prove an indication of line polarity;
• and comparison means connected across said telephone lines for generating a first output signal if said line voltage is within predetermined limits and a second output signal if said line voltage is without said predetermined limits.

A telephone line testing circuit comprising:

• means for connecting the circuit to a telephone line;
• polarity indicating means connected to said connection means for providing an indication of the telephone line polarity;
• comparisopn means connected to said connecting means for providing an indication of the telephone line voltage;
• and means connected to said connecting means for providing an indication of ground fault on said telephone line.