Abstract: A gas sensor includes a pair of lead strips, a sensing element preferably comprised of a metal oxide semiconductor, such as SnO.sub.2, and extending between the pair of lead strips in the form of a bridge, a heater driver for supplying a heating current to at least one of the pair of lead strips, a detector for detecting a predetermined property of the sensing element, and a control circuit for controlling the operation of the heater driver and the detector. In one form of the invention, the detector is activated in a time period in which the heater driver is not activated. In another form of the invention, the pair of lead strips are connected in parallel or in series when the heater driver is to be activated. In a further form of the invention, the heater driver is normally operated periodically, but when the detector first detects a predetermined condition, the heater driver is operated continuously.

Abstract: A remote meter reading arrangement in which power for the remote terminal is supplied from the data collection terminal by transmission lines. At the moment power is applied to the remote terminal, a clock pulse generator in the remote terminal is supplied with power and begins to generate clock pulses to a counter, which successively couples each stage of the meter to the data collection terminal so that pulses of greater or lesser amplitude are generated in sequence, corresponding to each significant digit of the remote meter, to indicate the meter reading.

Abstract: A remote meter reading unit (22) feeds clock pulses to a meter (23) over a transmission line (34). The meter (23), in synchronism with the clock pulses, feeds a predetermined number of synchronization signals, a predetermined number of meter data signals and a predetermined number of redundancy signals back to the reading unit (22).

Abstract: A remote meter reading system in which clock pulses are transmitted to a selected remote terminal to charge a capacitor there which acts as the terminal power supply. Subsequent clock pulses reset a ten-stage bit counter and four-stage digit counter, after which additional clock pulses step the bit counter, the outputs of which are AND-gated with the outputs of the digit counter, in such a manner that the current drawn from the central data collection terminal is increased whenever there is coincidence between the bit counter and digit counter outputs. A counter at the central data terminal is stepped by the clock pulses and disabled by the relatively large pulses developed when the bit and digit counter outputs coincide. Therefore, the output of the central data terminal counter corresponds to the desired meter reading.

Abstract: A data collection system wherein a metering center or central metering station sequentially selects a large number of remote terminal equipment block selectors and through the selected selector sequentially selects a plurality of terminal equipments or meters each for each comsumer belonging to the selected selector whereby the data or readings of the meters may be sequentially read into the metering center. The combinations of two coded signals are used for the selection of the terminal equipment block selectors while one code signal is singly used for selecting one of the terminal equipments. According one aspect of the present invention the terminal equipments having special instruction codes recorded therein are inserted into the groups and blocks to facilitate the switching of readings from one group or block to another.