The 4001 option is designed to be added to a standard OS4000 Digital Storage Oscilloscope to enable the information in store to be retransmitted in both analogue and digital form. Two analogue outputs are provided, and these are intended primarily to drive strip chart and X-Y recorders. Channel 1 and 2 signals are available simultaneously at a read-out rate which can be varied to suit the chart recorder, with a slowest time of 200 seconds representing the 10 division display. In addition, a corresponding X-ramp signal is provided for X-Y recorder use. The unit also incorporates relay contacts for pen lift or chart motor control. There is a variable delay between the closing of these contacts and the start of read out which can be preset to allow a chart drive motor to accelerate. A socket on the rear panel presents the output information in digital form as two eight bit parallel signals for Y and one ten bit parallel signal for the X ramp. Control facilities for remote start and continuous readout are also provided. The latter can be used for continuous generation of a recorded transient or frequency shift of recorded waveforms.