B channel
![](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/S0_Rahmenstruktur.svg/220px-S0_Rahmenstruktur.svg.png)
B channels at the S 0 interface of the basic connection
A B-channel ( English : bearer channel , "carrier channel") is the channel for the transmission of user data (for example voice) in ISDN . A B-channel is therefore also referred to as a useful channel . A B-channel offers a bit-transparent and synchronous connection to another participant with a data transfer rate of 64 kbit / s ( full duplex ). It is used for direct communication between subscribers and not, like the D channel , for the exchange of signaling information between the terminal and the exchange .
In Europe, an ISDN basic connection has two B channels and an ISDN primary rate connection has at least 16 and a maximum of 30 B channels.
In a GSM network, the traffic channel corresponds to the B channel.