Rutgers Physics Student Response System
The Signal Distributor
The computer by which the instructor interacts with the SRS system is
located at the lectern in the front of the lecture hall. Electrical
connections to the seats must run through a long and not very thick
conduit. The commercial parallel I/O board for the computer is not designed to
drive long wires, so the controller had to be placed in the lectern as well.
Thus the connections from the controller to the rest of the system
needed to be kept to a minimum, but had to
be suitably driven long wires, requiring differentially driven pairs.
We settled on a 24 pair cable with 13 unidirectional signals from the
controller, and 8 bidirectional signals. A signal distributor was necessary
to send these signals to the six substations. In addition to acting as a
buffer, the distributor multiplexes the row inputs further, with three
substations being multiplexed into the lower four bits, and three into the
upper four bits, of the bidirectional 8 bit line which also carries the
light-enable signals from the controller.
Due to the large number of wires incoming to the distributor, it was
implemented on four printed circuit boards, one handling the lines to
and from the controller, one the control cables to the substations, and
one for each set of three substations for the individual substation
cables.
More details of the signal distributor:
[Please note: the signal distributor was previously called Boss1. This name
appears in the references above].
Revised: August 5, 1996.
shapiro@physics.rutgers.edu
