. This basic bit rate is designated E0. The
E interfaces are documented by the International Telecommunication Union(ITU) as G.7xx.The individual interfaces (E1, E2, E3
, E4, and E5) correspond to a multiplex hierarchy in which the higher-order interface forms the 4-way multiplex of the lower-order interface:Four E1 lines
are multiplexed to form an E2 channel, four E2 channels are multiplexed to form an E3, four E3 lines are multiplexed to form an E4 channel, and four E4 channels are multiplexed to form an E5 channel.An E1 transmission link consists of 32 transmission channels at 64 kbit/s each, corresponding to a total transmission rate of 2.048 Mbit/s
.user data. This reduces the bandwidth for the user data to 1.920 Mbps. This corresponds to a bandwidth utilization of 93.8 %. Channel 0 provides a unique bit pattern for synchronization and also indicates transmission errors. Channel 16 is used for signaling and is responsible for establishing and terminating connections for the individual user channels. The coding of the resulting bit stream is done in an HDB3 coding
.bits long, it consists of 4 subframes of 384 bits each. The E4 data transmission frame consists of 6 subframes with a length of 488 bits each.