Means for providing for yielding to a higher priority service in a telephone system

Claim 2

In a system including auxiliary apparatus utilizing the facilities of a telephone system for transmission of secondary data without interfering with the higher priority normal uses of said telephone system, the combination of: telephone means; telephone system means having an operative and a nonoperative connection to said telephone means for transmitting signals from one selected location to another; auxiliary apparatus for producing secondary data signals, and for transmitting said secondary data signals over said telephone system means; signal producing means located remotely from said telephone means and being responsive to the operative connection of the telephone system means to the telephone means to produce a signal indicative of a need to use said telephone system means in conjunction with said telephone means for transmission of telephone communication signals; and circuit means for providing a first mode of operation in which said telephone system means is operatively connected to said telephone means for transmitting normal telephone communication signals and for providing a second mode of operation in which said telephone system means is operatively connected to said auxiliary apparatus for transmitting said secondary signals, said circuit means being responsive to said signal producing means to cause a change from said second mode of operation to said first mode of operation.

Claim 3

The invention as defined in claim 1 in which said auxiliary appaRatus comprises meter reading means for reading utility meters and for producing signals indicative of the meter reading thereby obtained.

Claim 4

In a meter reading system utilizing telephone lines: a test circuit comprising a telephone and a meter reading apparatus connected in parallel relation across said telephone lines, said meter reading apparatus having a relatively high impedance and said telephone having a relatively low impedance when connected ''''line''''; meter reading excitation means for applying a voltage to said test circuit, which voltage varies over a substantial range; impedance testing means for determining whether said telephone is connected ''''on line'''' comprising, reference circuit means having an impedance between that of said telephone and that of said meter reading apparatus, said reference circuit being subjected to a voltage from said excitation means which is variable with said voltage applied to said test circuit; and current sensing and comparator means for comparing the current flow in said test circuit with the current flow in said reference circuit and for providing a third output indicative of the state of comparison to indicate whether said telephone is ''''on line.''''

Claim 5

In a meter reading system utilizing telephone lines: a test circuit comprising a telephone and a meter reading apparatus connected in parallel relation across said telephone lines, said meter reading apparatus having a relatively high impedance and said telephone having a relatively low impedance when connected ''''line''''; meter reading excitation means for applying a voltage to said test circuit, which voltage varies over a substantial range; impedance testing means for determining whether said telephone is connected ''''on line'''' comprising, reference circuit means having an impedance between that of said telephone and that of said meter reading apparatus, said reference circuit being subjected to a voltage from said excitation means which is variable with said voltage applied to said test circuit; and current sensing and comparator means for comparing the current flow in said test circuit with the current flow in said reference circuit and for providing a third output indicative of the state of comparison to indicate whether said telephone is ''''on line.''''

Claim 6

The invention as defined in claim 3 together with switching means responsive to said third output for disconnecting said excitation means from said test circuit when said telephone is connected ''''on line.''''

Claim 7

The invention as defined in claim 3 in which: said meter reading apparatus exhibits a breakover impedance characteristic in that substantially no current flows therethrough until a predetermined excitation voltage is exceeded; and said reference circuit includes a breakover device to give said reference circuit a breakover impedance characteristic in that substantially no current flows therethrough until said excitation voltage exceeds a predetermined level.

Claim 8

The invention as defined in claim 5 together with switching means responsive to said third output for disconnecting said excitation means from said test circuit when said phone is connected ''''on line.''''

Claim 9

In a system including auxiliary apparatus utilizing the facilities of a telephone system for transmission of secondary data without interfering with the higher priority normal uses of said telephone system, the combination of: telephone means; telephone system means having an operative and a nonoperative connection to said telephone means for transmitting signals from one selected location to another, said telephone system means also having a first impedance level when the telephone system means is nonoperatively connected to the telephone means and a second impedance level when the telephone system means is operatively connected to the telephone means; auxiliary apparatus for producing secondary data signals and for transmitting said secondary data signals over said telephone system means; signal producing means responsive to the change from the first impedance level to the second impedance level of the telephone system means to produce a signal indicative of a need to use said telephone system means in conjunction with said telephone means for transmission of telephone communication signals; and circuit means for providing a first mode of operation in which said telephone system means is operatively connected to said telephone means for transmitting normal telephone communication signals and for providing a second mode of operation in which said telephone system means is operatively connected to said auxiliary apparatus for transmitting said secondary signals, said circuit means being responsive to said signal producing means to cause a change from said second mode of operation to said first mode of operation.

Claim 10

In a system including auxiliary apparatus utilizing the facilities of a telephone system for transmission of secondary data without interfering with the higher priority normal uses of said telephone system, the combination of: telephone means; telephone system means having an operative and a nonoperative connection to said telephone means for transmitting signals from one selected location to another, said telephone system means also having a first impedance level when the telephone system means is nonoperatively connected to the telephone means and a second impedance level when the telephone system means is operatively connected to the telephone means; auxiliary apparatus for producing secondary data signals and for transmitting said secondary data signals over said telephone system means; signal producing means responsive to the change from the first impedance level to the second impedance level of the telephone system means to produce a signal indicative of a need to use said telephone system means in conjunction with said telephone means for transmission of telephone communication signals; and circuit means for providing a first mode of operation in which said telephone system means is operatively connected to said telephone means for transmitting normal telephone communication signals and for providing a second mode of operation in which said telephone system means is operatively connected to said auxiliary apparatus for transmitting said secondary signals, said circuit means being responsive to said signal producing means to cause a change from said second mode of operation to said first mode of operation.

Claim 11

The invention as defined in claim 7 in which said auxiliary apparatus comprises meter reading means for reading utility meters and for producing signals indicative of the meter reading thereby obtaIned.

Claim 12

The combination comprising: first and second transmitting circuits each having an operative condition; first circuit means connected to the first and second transmitting circuits and being effective to provide a communication circuit for said first and second transmitting circuits, said first circuit means having a first current level flowing therein in response to the operative condition of the first transmitting circuit and a second current level flowing in response to the operative condition of the second transmitting circuit; signal producing means located remotely from the first and second transmitting circuits and having current of a predetermined level flowing therein, said signal producing means being effective to compare the current levels of the first circuit means with said predetermined current level and provide an output signal indicative of the state of comparison between the current levels; and second circuit means responsive to said third output signal to remove the first transmitting circuit from its operative condition.

Claim 13

The combination comprising: first and second transmitting circuits each having an operative condition; first circuit means connected to the first and second transmitting circuits and being effective to provide a communication circuit for said first and second transmitting circuits, said first circuit means having a first current level flowing therein in response to the operative condition of the first transmitting circuit and a second current level flowing in response to the operative condition of the second transmitting circuit; signal producing means located remotely from the first and second transmitting circuits and having current of a predetermined level flowing therein, said signal producing means being effective to compare the current levels of the first circuit means with said predetermined current level and provide an output signal indicative of the state of comparison between the current levels; and second circuit means responsive to said third output signal to remove the first transmitting circuit from its operative condition.

Claim 14

The invention as defined in claim 9 further comprising excitation means for applying simultaneously variable voltages to both said first circuit means and said signal producing means whereby current flows in the first circuit means and signal producing means.

Claim 15

The invention as defined in claim 10 wherein said second circuit means comprises switching means for disconnecting the excitation means from the first circuit means.

Claim 16

The invention is defined in claim 9 wherein said signal producing means comprises: a reference circuit having current of a predetermined level flowing therein; first current sensing means for sensing said levels of current flow in said first circuit means and providing a first output signal indicative thereof; second current sensing means for sensing the level of current flow in the reference circuit and providing a second output signal indicative thereof; and comparator means for comparing said first and second output signals and providing a third output signal indicative of the state of comparison between said first and second output signals.