A Fault Tolerant Dial Router (FTDR) includes redundant subsystem resources that operate independently of telephone line interface connections. The redundant resources are switched active when a failure is detected in an activated dial router subsystem. Switching out subsystem failures is fully automated under software control, providing uninterrupted service to users with limited performance loss. The FTDR includes a switching mechanism that selectively switches out the telephone interfaces or other subsystem resources inside the dial router box detected as having failures. The subsystem resources include line framers, controllers and modem modules.