for 20 residential units, flush-mounted installation, front plate 3 mm, win:clip principle, name field size: H 19 mm x W 62 mm, metal bell buttons with gold-plated, maintenance-free contacts, long-lasting and energy-saving name / information plate lighting, shatter-proof name plate glass, acknowledgement tone when the bell button is pressed, perforated intercom grille, front plate: polished stainless steel, 3-wire technology required, permissible ambient temperature: -20 degrees C to 50 degrees C, dimensions front plate: H 340 mm x W 274 mm x D 3 mm, dimensions flush-mounted box: H 291 mm x W 250 mm x D 40 mm