BWD 820 Portable Oscilloscope provides an accurate measurement capability from DC to <25MHz with a sensitivity range from 2mV to 20V/cm and selection of either normal dual channel or a single channel differential operation. Time-base and trigger facilities complement the vertical amplifiers with a 40nSec to 5 Sec/cm sweep range and triggering from 2Hz to 40MHz. Operation is virtually automatic with the BWD "all buttons out" feature for normal dual trace operation. Changeover from chopped to alternate display and frame to line video triggering is controlled by the time-base range switch. Calibration accuracy is maintained within 3% over widely varying conditions of temperature and supply voltages by electronically regulated supplies throughout. High brightness, even with low repetition rate signals is provided by the 4kV EHT supply for the high definition mesh PDA CRT. Identical X-Y sensitivities, phase compensated from DC to 100kHz are incorporated for phase measurements of amplifiers, filters, etc. A DC coupled TTL compatible Z modulation input enables the BWD 820 to be applied to digital measurements and display video readouts as a DC coupled X-Y-Z monitor. The regulated supplies and low power consumption, together with the high stability of the integrated circuit amplifiers reduces drift or trace movement to a very low level in both monitoring and measurement applications. For TV or VTR applications, an active sync separator ensures stable video displays with polarity selection and automatic changeover from frame to line. An additional feature of the TV trigger is as an AM demodulator to lock modulation waveforms and as a filter when measuring noisy signals. The BWD 820 is designed to closely conform to I EC 348 recommendation and has been subjected to a wide range of environmental conditions to ensure a reliable long life. Its advanced low power consumption circuitry employs both analogue and digital I.C.'s and a DC to DC switching converter power supply. No ventilation holes are needed, due to the low temperature rise, thus minimising dust ingress. However* like all electronic instruments, it is advisable to store it out of direct sunlight to minimise temperature cycling.