A method and system for feedback circuit design are disclosed. In a first embodiment, an optical attenuator and two variable chromatic dispersion devices are used for imparting an attenuation and positive and negative chromatic dispersion, respectively, for an optical signal propagating from an input port to an output port of the optical network simulation apparatus. In another embodiment arms press against the ends of the sod rolls exerting pressure on them to retain them for pick up. The states of the switches are communicated to the device through a mechanical connector or a wireless communication channel as a corresponding command, and the user interface reacts accordingly. The control circuit controls the switches in the switching circuit to be turned on for an adaptive constant time, and be turned off for a minimum time. The features of an email message include multiple words usually associated with email messages.