The SD24 is a dual-channel TDR/Sampling Head. This sampling head has a rise time of 17.5 ps or less, with a typical 20 GHz equivalent bandwidth. Each channel of the SD24 is also capable of generating a fast rising step for use in Time Domain Reflectometry (TDR). In TDR mode, the acquisition portion of the sampling head monitors the incident step and any reflected energy. The reflected rise time of the TDR step is 35 ps or less. The polarity of each channel's TDR step can be selected independently of the other channel. This allows for differential or common-mode testing of two coupled lines, in addition to the independent testing of isolated lines. The SD24 can be used to characterize crosstalk by using the TDR step to drive one line while monitoring a second with the other channel. The %22filter%22 function on the CSA803C/11801C can be used with TDR or crosstalk measurements to characterize a system at a slower rise time.