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SCS SEN4137091 Metallic Door Phone Kit Mounted in Brackets 2 Wires Included - - Amazon.com
Urmet Intercom Set 1122/31 2-Wire Set Door Intercom Set, Complete Set (Ring, Talking, Hearing, Opening Door) Bell Mute, Turn Your Bell with 2 Wires into a Complete Intercom System : Amazon.de: DIY