Belt reader
The belt reader is a building used to detect the flow of items. The average rate over the last 10 seconds is displayed in the center of the building, in items per second. Additionally, there are two wire outputs. The right outputs true 
if any item has passed in the last second, false 
otherwise; importantly, this means that it will read false if completely backed up as well. The last item to travel through the belt reader will be output as the right signal. Unlike the storage, this signal remains even after the reader empties.
Uses
Typically, belt readers are used for the boolean output, such as in item counters, used for freeplay dump systems. If a quicker response time is needed, such as in certain clock circuits, alternating items passed through the reader will generate an alternating signal on the left output.
Known issues
- The belt reader is known to sometimes have an adverse effect on throughput, most notably connected to belt corners. Therefore, using readers to debug factory lines can, counterintuitively, create more flow issues than they solve.
- The numeric display occasionally misreports the actual speed due to rounding errors.