OK, we may have a solution! It looks like Rick was on the right track when he suggested that a faulty cable could create noise thereby simulating pulse dialing.
Yesterday, I changed the extension number of the telephone most often experiencing the problem from 111 to 181. (This is only a 2 wire circuit feeding a standard telephone at one of the houses on the compound.) I then assigned extension 111 to the telephone on my desk. This is a Panasonic KX-T7030 telephone which will display the extension of the person placing the call. This morning, the problem did indeed occur on my telephone. It showed that the person calling was at extension 172. This is a vacant house. When I checked this line, I found that it is shorted and quite noisey. So, for now, I have disconnected this line from the PBX. I think this will probably solve the problem.
So, I would like to say thank you to everyone for your ideas. I greatly appreciate your assistance!
David Creel
P.S. Thanks for the link, Ed. I bought a "new in the box" serial to parallel interface on eBay. Once it arrives, I plan to connect a printer and use the SMDR feature. This should make future troubleshooting much easier! Thanks for the idea, KX-TDA.
