A back-to-back connection is the direct connection of the output of one device to the input of a similar or related device.
The back-to-back connection eliminates the effects of the transmission medium.
A back-to-back connection for electric power transmission is a high-voltage direct-current (HVDC) system with both ends in the same switchyard.
This is used to couple asynchronously operated power grids or for connecting power grids of different frequencies where no DC transmission line is necessary.
In electronics, a back-to-back connection is the connection of two identical or similar components in series with the opposite polarity.