A multiplex telegraph is a communication system that allows multiple messages to be sent simultaneously over a single telegraph line. This technology improves efficiency by maximizing the use of existing telegraph infrastructure, enabling faster communication across long distances. Developed in the 19th century, multiplex telegraph systems often used techniques like time-division or frequency-division multiplexing. These methods allowed operators to send different signals at the same time without interference. The invention of the multiplex telegraph was a significant advancement in telecommunication, paving the way for modern communication technologies like telephone and internet.