What is the method of passing electrical and communications signals from one car to another?

The method of passing electrical and communications signals from one car to another is accomplished through the electrical portions in the coupler. This approach is essential for ensuring seamless communication and power transfer between connected train cars. The coupler is designed to facilitate the transmission of electrical signals used for various functions, such as signaling, control systems, and safety mechanisms. By integrating electrical components into the coupler, train systems can maintain operational integrity and streamline communication across multiple cars.

Considering the other options, while friction brake systems and manual control panels play roles in train operation, they do not inherently facilitate the direct transfer of signals between cars. Wireless communication can also transmit signals, but the question focuses on a physical connection method specifically designed for train car interactions. Therefore, the electrical portions in the coupler represent the most accurate and traditional method for passing these signals between cars.