Bogen TEL1S Telephone Input Module (for Bogen Matrix Systems)Bogen's advanced plug in modules provide a wide range of functions to support a variety of applications. These modules support different signal source requirements, including the ability to interface to balanced and unbalanced high and low level inputs, stereo or mono, telco systems, and microphones. Features: Loop start or ground start trunk interfacing (requires external power supply) Dry loop interface to paging ports Audio activated paging in dry