Rutgers Physics Student Response System
The Substation
Each substation controls up to eight subsubstations, and thus a maximum
of 128 student stations. In our lecture hall the substations are mounted
on the ceiling of the storage room under the seats of the lecture hall.
Each subsubstation is connected by a 15 conductor cable,
through a hole in the floor, to its substation.
The substation controlled by the signal distributor, to which it
is connected by two
cables of differentially driven pairs. One, which goes to all substations
in parallel, carries 17 control signals to the substations. The other
cable individually connects each substation to the distributor and carries
five signals, four row outputs and one LE latch input.
The substation provides
power and the polling lines (D0-D5) in parallel to all the subsubstations.
It receives the four row inputs from each, and multiplexes them according
to control signals (SS0-SS2) which it receives from the controller. The
four outputs of the multiplexer are sent to the distributor.
It also latches the eight light-enable signals, which are part of the
17 signal control cable, with the individual LE latch pulse.
More details of the substation:
Revised: October 10, 1995
shapiro@physics.rutgers.edu
