Sanchit Sharma presented a seminar on communication devices. The document discussed the history of communication dating back to 3200 BC, and outlined some key communication devices such as modems, routers, hubs, switches and mobile phones. It described that a modem modulates and demodulates signals to transmit digital data over phone lines or wirelessly. Routers make forwarding decisions based on IP addresses, while hubs and switches connect devices but switches make routing decisions based on hardware addresses. Mobile phones allow calling, texting and have additional features like cameras and web browsing. Bridges and repeaters were also discussed as connecting or boosting signals between networks.