A telephone call routing system for routing incoming telephone calls assigns each such incoming call to a selected one or more of a plurality of agent display modules. The agent display module has a visual output indicating which of a plurality of telephone lines carries the incoming call assigned to it. Any one of a plurality of agents' telephones associated with corresponding agents' modules may be connected to the line carrying the incoming call. Each telephone has a device for generating and transmitting a coded signal along the telephone line which is answered by that particular telephone. The signal is uniquely coded to identify the agent's module which is associated with the telephone which answers the incoming call. A signal detection device detects the transmitted coded signal and decodes the signal to determine which telephone associated with an agent's module answered the incoming call. A monitoring device monitors the agent telephone activity by determining and storing a characteristic representative of activity of each agent's telephone. The assignment of the next incoming call to one of more of the agents' modules is then determined by the extent of activity of each of the agents' telephones.