The tuner has constituent component for constructing a tunable or switchable spectral filter, including single and multiple stage filters and fitters without intermediate polarizer, over a wavelength range. The diamond body is formed from diamond grains and a catalyst material at high pressurehigh temperature conditions. The test device, under user control, may introduce jitter, drop packets, create new packets, reroute packets, and reorder packets in the conversations. A lubricating regulator valve is provided in a lubricating oil passage connected from the main regulator valve to regulate a hydraulic pressure in the lubricating oil passage to a given pressure in response to a driving state of the vehicle.