Existing digital automated test equipment (ATE) can provide signals at about 1 Gbps or slightly higher. To accommodate multi-GHz test needs, some ATE provide options for a few faster channels (up to 3.6 Gbps). However, leading-edge parts may require 100s of these signals and in some cases at even higher speeds (5 and 10 Gbps). This paper describes a modular approach that allows for as many as 144 multiplexing and/or sampling channels to be added to existing ATE. The modules developed, so far include multiplexers, demultiplexers, and high-speed samplers that each support multiple high-speed differential signals. Production units operating up to 2.5 Gbps were introduced in [10]. In this paper we provide more detailed characterization of these modules and describe new modules targeting 3.2 Gbps and 5.0 Gbps applications. Various re-clocking techniques and proprietary calibration methods are used in order to reduce timing errors (especially jitter) to the sub-50ps range. The general system configuration, and key features of the newly developed modules are presented.