Siemens U-MHU-MCS I believe that this alarm is capable of doing multiple tones. Brand SiemensModel U-MHU-MCSManufacturer SiemensType Alarm (Horn/Strobe)
Firecom FVA4-RC24D+FHA24D Category : OtherThis horn/strobe, which is made by Space Age Electronics, is meant as a replacement for their older AV32-series strobe plates.
Simplex 4904-9139 Category : SimplexI believe that this strobe plate was designed to be used with bells, such as the Simplex 2901-9333.