All members of the family ran one of three IBM-supplied programs.

The 3725 replaced the hardware line scanners used on previous 370x machines with multiple microcoded processors.

[3] With the expansion unit, the 3725 could support up to 256 lines at data rates up to 256 kbit/s, and connect to up to eight mainframe channels.

[9] Replacement software products are Communications Controller for Linux on System z and Enterprise Extender.

Several companies produced clones of 37xx controllers, including NCR COMTEN and Amdahl Corporation.