The APCS-1250A is the first fully integrated InGaAs/InP single-photon detector working at a gating frequency as high as 1.25GHz. This integrated single-photon detector obtains low dark count rate, low after pulsing probability and high maximum counting rate simultaneously. The detector can be trigged with internal/external clock reference, and output multiple independently programmable high-precision clock signals. Many parameters can be finely regulated, such as the gating amplitude, the voltage bias, the time delay of synchronized signal, the cooling temperature, the discrimination threshold, the programmable dead time. Additional monitors for avalanche signals are optional. Besides, the interaction interface is carefully designed and appears kindly to every user.