If you want to equip a BehiG-Komform switch, a hearing-impaired loop is essential (specifications in accordance with standard SN EN 60118-4: 2015 + A1: 2018).
Excerpt from the DETEC ordinance on the technical requirements for the disabled-friendly design of public transport: 151.342, Art. 5, Paragraph 7: In counter systems with intercom systems there is at least one switch with an induction amplifier for the hearing impaired to be provided and marked accordingly.
An induction loop, also known as a hearing loop or T-loop, is a supportive hearing aid that allows people with a hearing impairment to access facilities. It picks up a sound source and transmits it directly to a hearing aid without background noise. The presence of an induction loop should always be indicated by the symbol on the right.