For an oscilloscope capable of simultaneously displaying a plurality of waveforms on a screen and capable of performing operations with respect to a selected one of the displayed waveforms, a method and apparatus for permitting an operator to select a waveform. A touchscreen mechanism provides input signals to the oscilloscope indicating when and where an operator touches the surface of the screen and a microcomputer within the oscilloscope deter­mines from data controlling the display of each waveform and from the data provided by the touch­screen whether the operator is touching any portion of a displayed waveform. If so, the microcomputer assumes that the operator has selected the waveform touched and reconfigures oscilloscope operation such that operations are performed with respect to the waveform touched by the operator.

In a multiple trace oscilloscope wherein separate traces displayed on a cathode ray tube screen are updated in succession, a random access memory is addressed by the count output of a programmable counter which increments its count each time the oscilloscope finishes updating one trace prior to updating a next trace. Data stored in the random access memory at the storage location addressed by the count is utilized to control attributes of the next trace to be updated by controlling the switching positions of attribute control switches which select the horizontal, vertical and intensity control signals controlling the appearance of each trace.

A primary test and measurement device merges a primary (i.e., local) a non-primary (i.e., remote) waveform data to produce a display signal that, when presented on a display device, shows both waveforms. The primary measuring device may utilize respective transparent windows for each waveform such that the transparent windows may be overlaid during presentation to display waveform data from the non-primary measuring devices upon the primary measuring device. In this manner, a plurality of test and measurement devices are used to provide a single combined image for presentation.

A method of displaying a number of measurement curves is described. The measurement curves are displayed in at least two windows. Each one of the windows comprises two axes. One or more measurement curves are displayed in each one of the windows. The method comprises the steps of changing the scale of one of the curves in the direction of at least one of the two axes by a user and synchronizing at least one of the other curves of one or more other windows with respect to one of the two axes depending on said change carried out by the user.

A timing signal generating circuit (2c) generates a timing signal for each sweep timing dot. An address generating circuit (2a) generates an address corresponding to each sweep timing dot and to the magnitude of an input signal, each time it receives the timing signal. An image memory (3) stores data in the address generated by the address generating circuit (2a). A computing unit (2b), upon each recepit of the timing signal, performs a predetermined computation on that data stored in the image memory (3) and generates a result of computation. The computation result reprsents the frequency of the same address generated for each sweep timing dot. A display unit (4) displays the input signal with a luminance level corresponding to the computation result.

For an oscilloscope capable of simultaneously displaying a plurality of waveforms on a screen and capable of performing operations with respect to a selected one of the displayed waveforms, a method and apparatus for permitting an operator to select a waveform. A touchscreen mechanism provides input signals to the oscilloscope indicating when and where an operator touches the surface of the screen and a microcomputer within the oscilloscope deter­mines from data controlling the display of each waveform and from the data provided by the touch­screen whether the operator is touching any portion of a displayed waveform. If so, the microcomputer assumes that the operator has selected the waveform touched and reconfigures oscilloscope operation such that operations are performed with respect to the waveform touched by the operator.