User:XtraJovial/JRH 721

Batches 1–5
The first four 721 series batches were built between 1988 and 1991, consisting of 22 three-car sets (F-1 – F-22). In 1992, in preparation for the Chitose Line extension to New Chitose Airport Station, a fifth batch, comprising 7 three-car half-sets (F-23, F-101–103, F-201–203), was built and arranged to form six-car sets. Fourth-batch set F-22 was combined with set F-23.

From 2001, these sets (excluding sets F-1 – F-14) were upgraded to allow for 130 km/h operation. These sets are designated as series (721系3000番台).

Batches 6 and 7
These batches were introduced between 1993 and 1994 and feature GTO thyristor-based VVVF traction control, comprising 9 three-car sets. They are designated as series (721系1000番台).