BCD Audio's involvement with PPMs started in 1995 with the BCD 950429 stereo drive card. This has balanced inputs and precision rectification which passed the level to a micro, where calibration, attack/decay, overload and sum/difference switching is implemented. The drive to the meter is by pulse width modulation (PWM) as the micro did [ read more ]

The PPM meter, with the black background and the white scale from 1 to 7 was a standard in UK Broadcast for decades. It was used to establish audio transmission levels and line up. Each scale number from 1 to 7 represents 4dB, with PPM4 corresponding to 0dBU and PPM6 corresponding to 8dBU. [ read more ]