The pyroelectric voltage response to rectangular signals of infrared radiation is derived using our recent analysis of the response to a step signal. The response is symmetrical with respect to the electronic and thermal time constants, τe and τT of the samples, and with respect to the times T1 and T2 of irradiation and darkening. When τe differs appreciably from τT, the rise of the response at the onset of irradiation and its fall at the beginning of darkening are exponentials with the same time constant, which is the smaller one from among τe and τT. A rectangular response is obtained when τe ≪ (T1, T2) ≪ τT. In this case the peak-to-peak value Vptp of the response is proportional to τe and independent of the pulse frequency, as well as of the ratio T1/T 2. When T1 and T2 are each less than the smaller one from among τe and τT, triangular responses are obtained, for which Vptp is independent of τe and inversely proportional to the pulse frequency. Pyroelectric responses obtained in triglycine sulphate and strontium-barium niobate samples of different τT were found to follow the derived expression, and plots of the measured parameters of the response vs τe, T1/T2, and pulse frequency show good agreement with the analysis.