Some Rigol scopes that support digital channels are not marked as having this feature. For example the DS1074Z Plus (defined on line 275 of `rigol-ds/api.c`) and DS1104Z Plus (defined on line 276). References: * https://sigrok.org/gitweb/?p=libsigrok.git;a=blob;f=src/hardware/rigol-ds/api.c;h=6846068965c4b9a31aa13de4786ee57ade64f4d2;hb=HEAD#l275 * https://int.rigolna.com/products/digital-oscilloscopes/1000z/ * http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-0504/1/-/-/-/-/MSO1000Z_Datasheet.pdf