WHAT IS DXC, CROSS CONNECT?

WHAT IS CROSS CONNECT?

Cross connect is the most important operation over SDH and MUX devices. Cross Connect will be referred to as DXC later in this document.

As explained in the previous sections, SDH and MUX devices are devices that allow small data channels to be transported through larger capacity data channels.

DXC IN MUX DEVICES

MUX devices use 2Mbps (E1) data channels as output. E1 data channels are the output data channels for MUX devices.

The E1 data channel consists of 32 64Kbps smaller data channels. In other words, 32 smaller data channels are carried in E1.

The 32 smaller data channels in each E1 signal have a name and these data channels are sequential. The first small data channel is called TS0 (Time Slot Zero), while the last small data channel is called TS31.

DXC in MUX Devices
As can be seen in the picture above, the E1 signal has 32 small data channels in 32 consecutive rows. This E1 signal is at the output of the MUX device. The 64Kbps data channels at the input of the MUX device are connected to the TSs in this E1 signal. This connection process is called DXC (Cross Connect).

TS0 and TS16 in the E1 signal are usually not used for small data channels, these TSs are used for signaling. In some cases these TSs can also be used.

The use of TS0 and TS16 for signaling leaves 30 user TSs in an E1 signal. 30 TSs means that 30 telephones can be carried on one E1 channel.

DXC in MUX Devices
The picture above shows a simple DXC example. The green phone connected to the MUX is placed in TS2 in E1. This placement is called DXC (Cross Connect). In the same way, the purple phone is placed in TS30.

This placement is done on the MUX device and this process is called cross connect.

By performing the same operation on both muxes, phones with the same TSs can communicate with each other.

BIDIRECTIONAL COMMUNICATION OVER MUX (BI-DIRECTIONAL)

MUX devices carry the collected small data channels to the SDH devices via E1 signals with a capacity of 32 small channels.

The E1 beacons, which are the output of the MUX devices, can be compared to a round trip highway. Within each E1 marker there are 32 arrival lanes and 32 departure lanes. The first arrival lane and the first departure lane constitute TS0.

Bi-directional Communication via MUX
As shown in the picture above, each TS has an incoming and an outgoing channel. Incoming channels are called RX and outgoing channels are called TX

Thanks to the RX and TX channels, information can be sent and received at the same time.

An example of the operation of the RX and TX channel is a phone call over a MUX. When making a phone call over MUX, your voice is carried on the TX channels of the MUX device and the sound you hear is carried on the RX channels of the MUX device.