FXO/DAA Design Using Clare OptoMOS Components for 911 Function, Consider the case of the satellite set-top box

Consider the case of the satellite set-top box. The STB periodically dials out to transfer information with the service provider. During this call, other devices like telephones connected to the telephone line cannot be used until the information transfer concludes and the DAA in the STB hangs up. This leads to the potentially dangerous situation where an emergency occurs during this period where the user needs to dial 911. The DAA in the STB must have the capability to detect when another phone or device tries to use the telephone line while the STB is already using the line