INTERCOM Video- and Audio Door Communication Sets. 2-WIRE TECHNOLOGY. Watch on the room monitor who is currently pressing the clock button on the front door, communicate while enjoying a quality call, and then simply open the door: GROTHE GmbH 2VOICE systems factory-prepared sets make door communication easy. Ordering is easy: you can order solutions for up to 42 apartments. Think about what you want, set your own criteria and quickly choose the right door communication set. Installing sets is as easy as choosing sets. It is also possible to order individual components separately.