He began his career as a military communications systems engineer troubleshooting voice and data information networks for the US Air Force throughout Europe from 1976 to 1981. He was later employed by Sprint Communications in a similar capacity until 1986 when he became the Director of the Network Control Center for LCI International (now Qwest Communications). In 1989, while still employed at LCI Mr. Denman was appointed to serve in the Office of the Chairman and was involved in strategic planning and mergers and acquisitions, which later led to his appointment as President of a small long distance operating company in Lima, Ohio that had been acquired by LCI, called Afford-A-Call. Mr. Denman served as the President of Afford-A-Call, growing sales to over $22 million before his departure in 1993.

From 1993 to 1997, Mr. Denman was a partner and owner of Impact Networking Solutions, a small telephone interconnect company serving Western and Central Ohio. Impact Networking Solutions sold small PBXs and Electronic Key Systems, along with local and long distance telephone service to small and medium size businesses. The company had hardware and network sales exceeding $4 million when Mr. Denman sold his interest in 1997. Impact Networking Solutions continues today with 2001 revenues exceeding $10 million from long distance sales alone.

From 1997 to 2000, Mr. Denman was a Director for Extant Corporation and was responsible for designing, engineering, implementing and monitoring a highly sophisticated national backbone network based on ATM (Asynchronous Transfer Mode) technology. Mr. Denman was responsible for building, staffing and overseeing the Extant Network Control Center and had direct responsibility for co-location equipment housed at several remote node locations throughout the United States. Extant was purchased in 2000 by energy conglomerate Dynegy Corporation.