It is antipicated that GREAT will frequently be used in conjunction with additional detector systems and a number of methods will be provided to enable data from these ancillary detectors to be combined with the data from the primary GREAT detectors.
In many ways the use of a TDR system makes this easier than with previous systems because there is fundamentally no event structure known to the electronics and so as long as data from the ancillary detectors includes the GREAT data tag the data can be handled.

It is expected that the following data sources could be accomodated by the GREAT Data Acquisition System.

• Purpose designed VXI electronics which are fully compatible with the GREAT VXI module standards and can use the same control and readout methods.

• VME data sources, including VXI modules, which can be read out by single cycle or block mode VME accesses.

• CAMAC adcs with FERA readout interfaced via the F2VB module.

• VXI electronics to the Eurogam standard which uses VXI backplane readout via the STR 8080 readout controller; DT32 bus and D2VB interface.

• Other data sources with DT32 output.

This list of possibilities is in order of ease of implementation and ease of connection to the primary VXI electronics with the first in the list being the most easy.

Multiple data sources place the following additional requirements on the readout system but these are almost automatic in a TDR system.

• Each data source must tag each data item or event fragment with the global data tag.
  
  
• All data sources which include buffering in the read-out mechanism must include a method to push data though the system so that it is available to the data handling software within a defined timeout period.