Terminal Guide

ANSI Charset Level 1 (ANSI_LEVEL_1)

ESC1B 20 L4c
xterm

Designate ASCII as G0, Latin1 as G1 and invoke G0 as GL and G1 as GR.

These sequences are not used in UTF-8 mode but only in traditional 7 or 8 bit ISO-2022 mode. See ECMA-043 for background.