The CALICE collaboration is developing highly granular
electromagnetic and hadronic calorimeters for detectors at future
energy frontier electron-positron colliders. After successful tests
of a physics prototype, a technological prototype of the Analog
Hadron Calorimeter has been built, based on a design and
construction techniques scalable to a collider detector. The
prototype consists of a steel absorber structure and active layers
of small scintillator tiles that are individually read out by
directly coupled SiPMs. Each layer has an active area of
72 × 72 cm^2 and a tile size of
3 × 3 cm^2. With 38 active layers, the prototype
has nearly 22,000 readout channels, and its total thickness
amounts to 4.4 nuclear interaction lengths. The dedicated readout
electronics provide time stamping of each hit with an expected
resolution of about 1 ns. The prototype was constructed in
2017 and commissioned in beam tests at DESY. It recorded muons,
hadron showers and electron showers at different energies in test
beams at CERN in 2018. In this paper, the design of the prototype,
its construction and commissioning are described. The methods used
to calibrate the detector are detailed, and the performance achieved
in terms of uniformity and stability is presented.