Abstract: A data receiver for transmitting interrogating signals to activate in sequence a plurality of data transponders, receiving data from the transponders, processing the data, correcting the data, storing the data in a temporary memory, and delivering the data to output equipment. Preferably, the transceiver may be used with a switched telephone network. Means are provided to detect when the telephone subscriber goes "off hook" and releases the line to the subscriber. The transceiver includes means to detect failure of response and stores signals indicating failures. Means are provided to transmit a second interrogation signal in a polarity opposite to the first to overcome the effect of a reversed subscriber line pair.

Abstract: A tone receiver for connection to a telephone line at the station end for responding to a predetermined tone frequency in which the receiver has a multiple frequency selectable channel for allowing the receiver to respond to only one of a plurality of input tone frequencies. Circuit means are provided for comparing the input tone frequency with the output of the selected frequency for insuring that the receiver is responsive to only a predetermined input frequency. A programming circuit is provided for allowing the receiver to sample the input tone frequency only during a predetermined time interval. Storage means are connected to and actuate the receiver output when a predetermined number of comparisons have been counted between the input tone frequency and the selected frequency of the receiver.

Abstract: A transponder for connection to a telephone line for transmitting data over the telephone line from one or more measuring transducers to a data collection center having input means preventing interference with normal telephone use but recognizing an interrogating signal which activates the transponder. The transponder includes a modulator circuit for transmitting data by a plurality of different frequencies which is actuated by a frequency control circuit for controlling the frequency output of the modulator. A bit line strobe counter is connected to the measuring transducers and the frequency control circuit for obtaining bit line data, and a dial line strobe counter is connected to the measuring transducers for sequentially obtaining data from the transducer dials. A program timing means is connected to the modulator circuit, the frequency control circuit, and the strobe counters for synchronizing the timing of the transponder.