The Model 655B features 8 reed relays. Each reed relay has a Form-A contact. These relays are designed to switch audio circuits on-and-off, or provide closures activated by a remote switch activation. All of the relays, on both models, are activated by applying ground to the appropriate control pin. By offering different models, the system designer can choose a unit that will fit the application perfectly. This will result in a more cost effective design. Also, the relay switching modules can be mixed and matched with other INTEGRA III SYSTEM cards, such as solid-state switchers, mixers and remote controls, within the same card frame.