TELEPHONE KEY SYSTEM by Metro Digital Resources Librarian • April 14, 2016 Similar in function to PBX but uses for small and medium-sized business applications. Key systems are used at the majority of the operating divisions and the ticket offices. Share:Click to share on Facebook (Opens in new window)Click to share on Twitter (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Tumblr (Opens in new window)Click to share on Reddit (Opens in new window)Click to email this to a friend (Opens in new window)Click to print (Opens in new window)Like this:Like Loading... Related