A multiplexer is another useful but not required hardware addition that is supported by the software. This allows rapid switching between different measurement directions and modes, i.e. front-to-back transmission followed by pulse-echo from the back side of the sample. While this is technically possible with only the pulser and oscilloscope, it requires manual rewiring for each change in direction or measurement mode. With a multiplexer, this change can be done quickly and automatically, enabling multimodal scans without user intervention. An example wiring diagram that enables all combinations of direction and transmission/pulse-echo is shown in Figure . Note that care must be taken when setting up multiplexed measurements to avoid directly connecting the pulser TX output to the oscilloscope. Excitation pulses are up to 300 V, which is well outside the safe operating range of the oscilloscope and will damage it. The software will check that a given module/switch combination for a measurement is safe, but this depends on the user-entered addresses matching the physical wiring.