MPC Data Protocol

AlphaCom support

The AlphaCom supports a subset of the MPC data protocol used with the classic Stentofon TouchLine exchanges. As it allows control of the AlphaCom exchange by mapping MPC commands to AlphaCom commands one-to-one it can be thought of as a variant of the simple link layer, but only for single-exchange (not AlphaNet) applications.

The output is broadcast of exchange events like dialled digits, station busy/free, connection and transfers. Note that it’s possible to send additional data strings from the AlphaCom’s Event Handler on this port also.

The TouchLine messages supported by AlphaCom are described in “Appendix: TouchLine Protocol in AlphaCom”, see page 83.

The original MPC protocol

The TouchLine (MPC) exchanges had a simple data protocol, initially output_only to send information to Intelligent Stations (LWT). The protocol was readable ASCII, in a broadcast mode, and no checksum. It was debugged by hooking up a VT100 terminal. Later on a data command input was added (which had a different format from the output messages).

The protocol was used for several purposes:

• Station emulation, i.e. digit dialing, M-key, handset, C-key (LWT, ITS, CRM, MLH) Monitoring of events related to this station (dialing to display, conversation partner, transfer destination, call request etc.)
• Monitoring of events related to many stations in the exchange (busy, program, line errors) Presented on DAKs (ITS) or screen (CHS)
• Additional functionality for the exchange, where an external computer would look for certain station actions, and take control from there (SVM)

The exchange has some functions purely for data communication, e.g. directory numbers with DigitDataTransmission ref-info which did nothing except sending out station keypresses.

Also, the data command X re-transmitted the incoming data on the broadcast output, thus allowing different data devices to communicate via the exchange (SVM updated DCB absence info).

The AlphaCom supports a subset of the MPC Data Protocol for backward compatibility. This allowed some TouchLine generation equipment like PNCI, MLH and CRM to be used with the AlphaCom.