KOI-7 (КОИ-7) is a 7-bit character encoding, designed to cover Russian, which uses the Cyrillic alphabet.
Shift Out (SO) and Shift In (SI) control characters are used in KOI-7, where SO starts printing Russian letters (KOI-7 N1), and SI starts printing Latin letters again (KOI-7 N0), or for lowercase and uppercase switching.
[2] KOI-7 was used on machines like the SM EVM (СМ ЭВМ) and DVK (ДВК); KOI-7 N2 was utilized in the machine-language of the Электроника Д3-28 [ru] (Elektronika D3-28) as four-digit hexadecimal code, БЭСМ-6 [ru] (BESM-6), where it was called ВКД, (internal data code).
Likewise, the IRV set in ISO/IEC 646:1991 also changed the character back to a dollar sign.
[6] In order to avoid conflicts with ASCII's and ISO 646's definition as DEL and its usage as EOF marker (-1) in some systems, it dropped the "CAPITAL HARD SIGN" Ъ that would have naturally resided at this location.