Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 12 Page 23 of 265
2.3 ST900 Controller Rack
Figure 4 – The ST900 Rack (General Arrangement)
Note that a standard 20A UK power distribution unit is shown in Figure 4; other
variants including a 30A variant and The LED variant of the distribution unit as well
as non-UK variants are also available.
The left-hand part of the rack contains the mains distribution unit (MDU) that
contains the logic power supply, the lamp supply relays, the maintenance sockets
and the controller’s power off/on switch.
Situated in the middle are the four 8-phase Lamp Switch cards, connected to each
other and to the Main Processor card by the phase bus ribbon cable connectors
across the front. Connectors on the back of the rack provide the mains connections
to the Lamp Switch cards. Each Lamp Switch card can control up to eight phases,
giving a total capability of 32 phases, with the first card being the one closest to the
Main Processor (i.e. on the right), with phase A at the top.
This leaves space to the right of the Main Processor card for any SDE/SA and/or
integral TC12 OTU cards (and/or IRM card in TfL cabinets). These cards are
connected to the Main Processor using an extended system bus cable that runs
along the back.