I'm going to assume you are talking about the Memorex Portable CD Boombox with AM / FM Radio (Model # MP 3851 SP), since you did not specify the model number in your question.
The Owner's Manual for this model can be found at the following link:
http://www.memorex.com/PageFiles/1019/manual.PDF
You may require a PDF Reader program installed on your computer to view this. You can download an excellent free one at
WWW.ADOBE.COM by clicking on the DOWNLOAD ADOBE READER button when you get there.
On page 6 of the manual you will see a layout of the buttons.
Page 10 describes the detailed button operations.
Button # 20 on the diagram is the PLAY / PAUSE button.
It is the largest circular push button on the top of the unit, to the right of the CD loading hatch.
The PLAY / PAUSE button is dual action. It will start the CD playing and pushing it again will PAUSE the CD from playing. Pushing the same button again will UNPAUSE the CD and it will continue playing from the point when you pushed the PAUSE button initially.
If you hit the STOP button or eject the CD from the unit after the PAUSE button is engaged, you will NOT be able to resume from where you paused it.
If you have any questions or require further asistance please comment back here on this page and I will endeavour to help you.
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Thank you.
Joe.