The punch block contains a row of 18 pins or punchesC16 for information and 2 for feeding the tape. At the selected intervals of time, the punch assembly is pivoted on a shaft at the bottom, so the punch, paper, and pins are moved toward the disks. Those pins that strike raised ridges on the disks are forced through the paper, punching neat round holes. The pins that do not strike ridges do not punch holes. This record reflects the position of the disks, which is proportional to the water stage, all as a function of time.
Electronic translators can convert punched tape records into suitable input for digital computers.
The most recent advances have been in the area of data loggers. This group of electronic instruments has evolved quickly over the last 10 years. Some type of transducer is required to sense the water stage with this type of recorder. Options range from a pressure transducer sensing water level in a stilling well to a pressure transducer on a bubbler system, to an angular transducer sensing shaft rotation on a float-driven system. This type of system is perhaps best suited to the transmission of data via satellite or microwave, providing a central control location with current water stage information.