They are responsible for routing and transmitting the audio from a street panel to the corresponding housing terminal and vice versa. Each of the decoder outputs are programmed with a 4-digit MDS address. This address identifies the housing terminal connected to each exit, differentiating it from the rest of the installation's terminals. When making a call from an entrance panel, the MDS address corresponding to the marked dwelling is generated, so that only the decoder that has a programmed exit with the generated MDS address will establish communication between the entrance panel and the dwelling.