This page contains answers to questions that are sent to me about calculators on a regular basis.

**Shall I send you a picture of a calculator for which no picture appears on the site?**- Please be aware that I only show images of calculators on rskey.org that are in my physical possession, i.e., part of the rskey.org collection. While pictures of rare models are always welcome with gratitude, unsolicited pictures will not be featured on the site.
**I have a calculator but I lost the manual. Can you help me?**- Probably not. I won't bite your head off if you ask, but a) I don't have manuals for all the calculators in my possession; b) the manuals I have are mostly paper copies, and I have neither the time, nor the stamina to make copies/scans on demand (as you can imagine, I get a
*lot*of requests); c) even if I have a manual scanned, I may be violating the manufacturer's copyright by sending you a copy. **Where can I find a manual for my HP calculator?**- For current models, why, contact HP of course! For vintage models, I recommend ordering a CD-ROM set from the Museum of HP Calculators; this CD-ROM set contains a near complete collection of all manuals for older HP models.
**Where can I find a manual for my TI calculator?**- Go to the TI Web site. They have the manuals for most of their current models available for download in PDF format. (You can also order paper copies.) Unfortunately, manuals for older models are not available.
**Where can I find a manual for my Casio calculator?**- Manuals for select Casio calculators are available for download at Casio's Web site. A number of Casio manuals are also available online at silrun Systems. For other, older models, you are advised to try and call Casio; several people reported success, as Casio was able to send them at least a photocopy of the requested manual. You can also try usersmanualguide.com.
**Where can I find a manual for my Citizen calculator?**- Some Citizen calculator manuals (actually, manuals for most of their contemporary models) are now available online at http://www.citizen-systems.co.jp/english/support/download/electronic/index.html.
**Where can I find a manual for my Sharp calculator?**- Sharp USA has a manuals Web site at http://www.sharp-usa.com/products/ProductOperationManuals/, and some calculator manuals are available here. More manuals can be found at the Sharp UK Web site: http://www.sharp.co.uk/Manuals.aspx. You can also try usersmanualguide.com. or better yet, Sharp Austria at http://esupport.sharp.at/html/om/index.php?ProdLine=30&TemplateLang=en.
**Where can I find a manual for my Radio Shack/Tandy calculator?**- You can find some manuals by searching the Radio Shack Web site: e.g., try http://www.radioshack.com/search/manualResults.jsp?kw=calculator+manual.
**Where can I find a manual for other calculator brands?**- I have no idea! Presumably you already tried contacting the manufacturer. Your next best bet is to keep an eye on auction sites such as eBay, just in case a manual shows up. (Unfortunately, it is a lot more common to see machines there without manuals than the other way around.)
**Where can I get my calculator or accessory serviced?**- For in-production or recently discontinued models, you need to contact the manufacturer. For older models, you're probably out of luck.
**Can you repair my old calculator or accessory for me?**- Technically, yes, but it's probably not a good idea business-wise. Repairing old machines is made more difficult than necessary by the fact that original replacement parts are no longer available. Substitutes need to be found or jury-rigged. Success cannot be guaranteed, and diagnosis and repair can take many hours. If I charged you the true value of my time, you'd end up paying many times the value of an equivalent new calculator. If I charged you less, it'd just not be worth my time.
**Can you provide advice for my calculator repairs?**- I wrote fairly detailed accounts of some of my repair "war stories", these are published right here on my Web site. For instance, look at my HP-25C or HP-91 pages.
**How do I multiply and divide complex numbers on my calculator?**- If your calculator has complex number support, you must consult your manual to find out how complex arguments can be entered. On all calculators, however, you can multiply two complex numbers, $a+b{\rm i}$ and $c+d{\rm i}$, by computing $(ac-bd)+(ad+bc){\rm i}$
*.*Dividing $a+b{\rm i}$ and $c+d{\rm i}$ is computed as $(ac+bd)/(c^2+d^2)+(bc-ad){\rm i}/(c^2+d^2)$. Or, you can use your calculator's polar/rectangular conversion functions and convert $a+b{\rm i}$ to $p(\cos q+{\rm i}\cdot\sin q)$, and $c+d{\rm i}$ to $r(\cos s+{\rm i}\cdot\sin s)$. The product of the two numbers is then computed as $pr[\cos(q+s)+{\rm i}\cdot\sin(q+s)]$, whereas the division can be calculated using $(p/r)[\cos(q-s)+{\rm i}\cdot\sin(q-s)]$. I.e., to compute the product, multiply the magnitudes and add the phase angles; for division, divide the magnitudes and subtract the phase angles. **Why are your calculator images defaced with a copyright/not for sale notice?**- Most people respect other people's work, even on the Internet. Some don't. In particular, some unscrupulous sellers on eBay and other auction sites used my calculator images without permission, without naming the source, and without making it clear to buyers that the picture is not that of the actual item being sold. The copyright notice is meant to serve as a deterrent, although lately, some eBay sellers began to blatantly use cropped versions of my images. Needless to say, when I come across such an eBay auction, I immediately request its removal through eBay's Verified Rights Owner (VeRO) program.