Single-Axis Linear Digital Readout SDS3-1 Machine Boring machine turning and milling machine digital display. SINO digital readout system (DRO) is a very famous brand in China and also all over the world. SDS3-1 DRO is a LED display DRO. It’s a small size DRO but with strong operation function, special for single axis measurement and position control. This model DRO is widely used on surface grinding machines. Display precision can be set at 5 micron or 1 micron with the linear scale used.