Rolls HR341 voice band audio processor. The is a completely analog unit, not a clock in it. It has an instert point for taking bandwidth control of a single microphone or a group if your mixer will allow. The 24dB/oct shelving filters can be set to minimize noise and limit the voice bandwidth. The notch filter can eliminate an annoying feedback fundamental The headphone jack can cut the speaker out, but not the unswitched out. The compressor is a soft knee optical type and help smooth out loud signals transparently. This is ideal in the insert of a mixer for complete control of a microphone. For bandwidth and dynamics control as well as some feedback suppression. The built in power amp is about 2watts and will drive most speakers. The speaker load switch on the rear is for loading tube type amps that hate not having a speaker load on their output, or on a solid state unit you can switch it off. T/S means tip sleeve. This comes with a transformer type A/C adapter (not shown) so no noise from that.