If a cordless phone has no dial tone, it could mean that the base for the phone has become unplugged. The wires should be checked to ensure that the telephone line is plugged into the base and that the base itself is properly connected to a working electrical outlet.
A cordless phone also may not work if it has not been properly charged. If the base unit is located near other appliances, this may also cause interference, in which case the base should be moved to another electrical outlet. If there is still no dial tone on the cordless phone, the phone can be reset to restore it to working order.