Rohde amp schwarz ho3500 series logic probe head for hmo oscilloscopes rohde amp schwarz 3594624702 the rohde amp schwarz ho3508 is an active 8 channel logic probe head for hmo oscilloscopes this logic probe is not coupled to a specific instrument and can be used with all ramps hmo oscilloscopes rohde amp schwarz ho3508 8 channel logic probe head for hmo oscilloscopes