Abstract: A system is provided in a circuit switched network data transmission link between a user terminal and a host computer in instances where the terminal is connected to the network by a single telephone line and the terminal user has subscribed to a telephone company service feature such as call waiting. The system includes an interface at the terminal location between the telephone line and the terminal equipment. During a data session the interface detects a call waiting signal and generates a user signal. If the user desires to take the incoming call and suspend a data session, the interface responds to the telephone receiver being lifted off-hook and communicates through the circuit switched network with an interface at the host end of the communication. The host interface is programmed to maintain the data session at the host computer during a suspension of the communication by generating a signal simulating a terminal location signal.