When used with an analog phone line, the Viking VR-1B will provide "ring" indication, "on the phone" indication and "message waiting" indication for both "stutter dial tone" and standard message waiting voltage. In this application the VR-1B connects directly to tip and ring. When used with electronic or digital phones, the VR-1B won't have you guessing which phone is ringing in busy offices. The flashing LED can be seen up to 100 feet away. The VR-1B connects directly to the electronic phone's speaker. When used with a headset, you can end those nagging interruptions that occur when associates' don't realize you are on the phone because you are using a headset. The VR-1B will flash on and off indicating to everyone that you are on the phone and you are not to be disturbed. The VR-1B installs in the handset/headset jack using an included "T" adapter.