An electron beam injector has been constructed to study the longitudinal beam physics in the University of Maryland electron beam transport experiments, including studies of longitudinal beam pulse compression and resistive-wall instability. The injector consists of a variable-perveance gridded electron gun followed by three matching lenses and one induction acceleration module. In the beam pulse compression experiment, it produces a 50 ns, 40 mA and 2.5 to 7.5 keV electron beam pulse with an approximately linear time-dependent velocity tilt. This beam will be injected into an existing 5 m long periodic transport channel with 36 short solenoid lenses. With the given beam parameters and initial conditions, the beam pulse is expected to be compressed by a factor of 3 or greater when reaching the end of the solenoid channel. In the resistive-wall instability experiment, the injector produces an electron beam pulse of 5 to 50 ns in duration, about 100 mA in current and a few kilovolts in energy. This beam will be guided into a resistive-wall channel of a couple of meters in length for study of the longitudinal resistive-wall instability. This paper reports on the design features and the general performance characteritics of the injector system including its mechanical, electrical, and beam-optical properties.