Jan Holmstrom, former non-exec chairman, is stepping down from the board immediately.
The current acting finance director, Mark Elliott, will be executive chairman to work closely alongside the chief executive officer, while a new chief executive is sought.
Elliot said today: "It is with regret that Jan has informed the board that he is not able to commit sufficient time to an executive role in view of his other engagements.
"Accordingly, he has resigned with our gratitude for his contribution during the past three years.
"During this time, the company has established itself as a leading supplier of CCTV to the transportation market, realised its freehold property and subsequently made a significant capital repayment to shareholders, and instigated a dividend policy."
Yesterday, the firm announced the appointment of Jamie Cumming as a non-executive director with immediate effect, replacing David Voss, who retired from the position.
Shares dipped 3.92% to 6.125p.