  The t0.technology Control and Readout System (CRS) is a modular microwave
control and readout system for mm-wave and radio astronomy, THz imaging, noise
radar, and superconducting qubit control. The configuration discussed in this
work implements firmware for readout of microwave Kinetic Inductance Detector
(KID) arrays. The CRS can operate 4,096 KIDs over 2.5 GHz of complex bandwidth
between 0-10 GHz, typically allocated across four independent RF chains at
1,024x multiplexing and 625 MHz of complex bandwidth each. Every CRS can
operate as a standalone unit or collectively within one or more
backplane-enabled subracks that distribute power, clocking, and
synchronization, scaling to an arbitrary number of channels. Each fully
populated subrack supports arrays of more than 65,000 KIDs. The signal
processing and control software supports recent innovations in multi-probe
measurements and dynamic feedback modes, which are described in (Rouble et al.
2024). The CRS has recently been selected as the new baseline readout system
for the proposed South Pole Telescope instrument, SPT-3G+. We present the
hardware design, firmware capabilities, open-source control and data
acquisition software, and the first laboratory characterization measurements.
