Your question about Siemens S30050-Q2026-X MD

The MD (Message Distributor) board in the Hicom 390.1/391.1 systems is used to multiplex and demultiplex data lines and HDLC paths between the central controller and the periphery. In one direction, the MD receives messages from the message buffer unit (Q2004) and multiplexes them on the input/output controller groups of the line trunk group (LTG). In the other direction, messages are received from IOCGs and demultiplexed by the MD before being passed on to the MBU.

In the incoming direction, one of the four channels of the IOCG can be switched to each of the two channels to the MBU.

In the outgoing direction, two data channels from the MBU must be switched to four dual LTGs each. Data channel 1 goes to LTGs 1, 3, 5, and 7, and data channel 2 to LTGs 2, 4, 6, and 8. Both channels can be run simultaneously.

The MD is duplicated, and is located in the IOC/CSN Multi shelf, although it is assigned to a Common Control Multi (CCM) shelf.