Women who feel unsafe or uncomfortable due to unwanted attention on a night out can simply go up to a member of staff in the bar or club and ask ‘Is Luisa there?'
The set phrase is a discreet way for women to ask for help. Staff can then act to protect the affected woman either by getting security staff involved, calling her a taxi or taking her to a safe place.
Participating venues – ten so far – will display posters and stickers in women's toilets explaining the code.
Winterthur has become the first city in Switzerland to introduce the scheme, which is already used in Germany.
Bars and clubs in parts of England – including Sheffield and Lincolnshire – have their own such system, with women told to ask for ‘Angela' if they are being sexually harassed.