1A4
The 1A4 is a 1-series vertical plug-in with four input channels and 50MHz bandwidth. The four channels are grouped into two groups of two channels. The 1A4 has a special "trace slaving" mode which, when used in a 547 mainframe, allows channels 1 and 2 to be displayed using the A time base, and channels 3 and 4 to be displayed with the B time base. This allows high-speed and low-speed signals to be displayed together, similar to what a dual-beam scope can do, but without some of the cost and complexity.