Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 12 Page 52 of 265
3.10 Serial I/O Card
The I/O card provides a rugged interface for up to 24 digital inputs and 16
changeover outputs for the connection of pushbuttons and above ground detectors,
or to provide a free-standing UTC Interface or for linking between controllers.
A sub-equipped variant of this card is also available, fitted with only 4 changeover
outputs. If the IC4 Configuration requires the 24 in / 4 out variant but one is not
available, then a 24 in / 16 out card can be fitted in its place.
The I/O card connects to the PHS or previous I/O card via a high-speed serial cable
through which the card also obtains its logic power supply.
3.11 Intelligent Detector Backplane
The Intelligent Detector Backplane provides an interface for up to 4 Loop Detector
Cards, each Loop Detector Card connecting to up to 4 loops.
The Intelligent Detector Backplane connects to the PHS or previous Intelligent
Detector Backplane via a high-speed serial cable through which the card also
obtains its logic power supply.
Note that the Loop Detector cards themselves are powered from a separate supply
– see section 3.14.7. The Loop Detector supply is cabled separately. This supply is
normally -24V DC from the HPU, but can be provided from a separate transformer.
A twisted ribbon cable provides the connection between the loop detector cards and
the road loops, via the loop termination card.