 AVIS: TIS Interface
This Project was submitted to Parallax by Mark Spencer
People who live in remote, rural areas know that communication is generally not a problem, rumors spread like wild fire. However, communication during an emergency is another matter. A few years ago, a devastating flood stimulated our community to set up a Traveler’s Information System (TIS) local radio station to support our emergency communications needs. Many of you are familiar with TIS radios; on our highways the signs that say, “TUNE TO AM 1610 FOR ROAD INFORMATION”, inform the traveling public of a station near by.
Recent fire experiences and the proliferation of “AMBER ALERT” child abduction notices have highlighted the need to expand the capabilities of our TIS. The local volunteer fire department, as first responders to traffic mishaps on our windy mountain roads, frequently have to restrict traffic flow around accidents. Informed motorists are safer drivers. The county has set up an emergency alert system (EAS) network to broadcast locally significant emergency information to the public at large (AMBER ALERTS, sever weather warnings, etc.). The EAS transmissions use the fire department repeater to send the messages to special receivers located at strategic facilities in the community, however the system depends on the general pubic to listen to their police scanners to receive the messages. We needed a way to tie the EAS and our fire department into the TIS so that messages could be transmitted to a broader segment of the population and the traveling public. An interface, based on Parallax’s Basic Stamp® microcontroller, between the TIS and the emergency service radio channels was the answer.
The TIS is controlled by a computer that is programmed through DTMF tones received by a telephone connection or a handset at the station. The circuit of the TIS interface monitors radios tuned to the local fire department VHF frequency for specific codes that allow the fire fighters and the EAS to remotely access the TIS and send commands to upload immediate emergency messages, capture the TIS loop, and continuously broad cast those messages until no longer needed.
 Along with the BASIC Stamp microcontroller, the TIS interface includes a DTMF receiver by Holteck (www.holmate.com) that decodes DTMF tones into a 4-bit code output that is interpreted by the BASIC Stamp microcontroller. The BASIC Stamp microcontroller is programmed to recognize a specific DTMF code to in-turn send MACROs commands via the stamp’s DTMFOUT command to the TIS computer. On-scene fire fighters send the abbreviated commands to the interface via the touch-tone buttons on their radio microphones to access the TIS and upload the critical message they want broadcast. The BASIC Stamp module also monitors the squelch line of the EAS receiver waiting for an activation. Once the EAS is activated, the BASIC Stamp module sends the appropriate MACRO to the TIS to capture the EAS message and continuously loop broadcast that message to the public.
The basic premise of the interface is to allow emergency responders to have simplified access to the TIS from the field. The inherent capabilities of the BASIC Stamp microcontroller make the parts count of the TIS interface low and the programming simple.
This enhanced capability to our TIS has greatly improved the flexibility of the system and will result in a better-informed community during the next emergency. |