The SAS Relay Interface provides easy installation of new off-road technology into an existing infrastructure.

The SAS-1 is a multi-lane traffic-monitoring sensor that has the processing capability to detect vehicles lane by lane and compute all pertinent traffic monitoring parameters. These parameters include vehicle volume, lane occupancy, and average speed. Once measured, these parameters are sent to a cabinet controller or other end user device at a specified update rate (or as polled) via a serial interface such as RS-232, RS-485, or RS-422. Using this messaging protocol takes full advantage of the processing capability of the SAS-1 to simplify communications and reduce the processing load of a cabinet controller. There are however, many traffic monitoring sites in place (or planned) and traffic counters which use the traditional controller interface approach of vehicle presence relay signals (i.e. Type 170 detector card files and controllers, auxiliary contact inputs for counters, etc.). As shown in the figure, the SAS Relay Interface is used with the SmarTek Acoustic Sensor (SAS-1) to provide physical vehicle presence relay signals to a cabinet controller or traffic counter.

To meet a variety of end user needs and "loop" site back fit requirements, the SAS-RI is available in two form factors. The shelf mount version (below on the left) and the Type 170 card version (pictured below on the right) of the SAS-RI connect to the SAS-CT using the supplied RS-232 cable (RJ-45 connector on both ends). The shelf mount version brings up to ten (10) relay signals out via a multi-conductor cable connected at the rear of the SAS-RI shelf mount unit. This cable is made up of ten (10) conductors (open collector) for ten (10) relay signals and one (1) common conductor (common emitter). Up to four (4) shelf-mount SAS-RI's may be stacked and connected to provide physical relay signals for up to four (4) SAS-1 units connected to a single home run cable. The type 170 card version is comprised of a SAS-RI Main Card and up to two SAS-RI Auxiliary Cards.

The Shelf-Mount (left) and Type 170 Card (right) versions of the SAS Relay Interface

For a Full Description of the installation and use of this interface, please download this  SAS Relay Installation.

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