Where it makes sense to divide the receipt of mail and door communication, separate letterboxes can be installed. They are available as classical pass-through letterboxes in two widths or as a version with a removal door at the front. In most cases, however, a suitable combination of letterbox and intercom system is available. Connecting letterboxes with a call button, door loudspeaker and video camera covers the key functions at the entrance to the building. All letterboxes do, however, have one comfort feature in common: the flap is cushioned and closes gently. Tiresome rattling is now confined to the past, and even if the wind should rise, the letterbox remains firmly closed. As a general principle, Siedle letterboxes are compliant with the European standard DIN EN 13724.