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.