(Skip to bottom line) (Executive summary)
Both single-digit Range (permitted scores 0,1,2,3,4,5,6,7,8,9, and X) and Approval elections can be handled by any kind of voting machine capable of handling multiple plurality elections, i.e. every voting machine in the USA, without modification. The underlying reason for this is Jan Kok's mathematical transformation. An extension of this method can also be used (as is explained in more generality here) to handle two-digit range voting elections (i.e. range 0-99 rather than 0-9) on plurality machines, but only if the voter's "X (intentional blank)" option is sacrificed. Here are examples of how sample ballots would look on different voting machine types, and here is a demo range election you can participate in yourself (try it!) a quicker demo and a version of the quicker demo that demonstrates what range voting would be like on a plurality-style voting machine.
Q. But, I asked some voting machine manufacturers "Do your machines support range voting?" and they said "No."
A. Try asking them this way instead:
With range ballots run on ordinary plurality voting machines, slots (e.g. "levers" on New York style machines) get "chewed up" 10 times faster than with plain plurality voting. (Assuming 10 allowed scores. With 100 allowed scores, 20 times faster. With L allowed socres for 1<L<10, L times faster.) Consequently if it is a large enough election or if there are too many elections, you'd run out of levers and more machines would be needed (or you'd have to use range voting with fewer levels). Which would not be so fun. On the other hand with say, optical scan machines, you'd instead "chew up those little pen-fill blobs on the piece of paper" which seems far less of a limitation. (Indeed, range voting on such machines actually strikes us as more convenient and clear than plurality voting.) Ditto with many kinds of punch card machines. So we are not saying range voting is wonderful to run on all plurality machines. We are saying, it can be done on every plurality machine in the USA, with varying levels of convenience or inconvenience depending on the machine type and the election. (The most inconvenience occurs on certain kinds of punch card machines, but fortunately these are rare and their use-fraction is declining.) We do not especially recommend running range elections in this style. We would much prefer to have voting machines specifically designed for range voting. However, because range voting can be done on plurality machines as a stopgap measure, that makes it a lot more smoothly adoptable than many other forms of voting, for example IRV and Condorcet, which simply cannot be done on many kinds of plurality machines.
Since you asked, there is a general "consensus" (The word "consensus" is from Andrew Gumbel's book.) being reached that precinct-based "optical scan" voting machines are (as of 2005) the best kind available measured by a combination of the following:
Sorry, considerably fewer kinds of present-day voting machines can handle them.
You might naively think something like "optical scan machines are just an optical input device connected to a computer. Therefore, we can program it to perform any kind of election. Unlike, say, mechanical-counter based lever machines, which can only be used for additive kinds of elections, such as range, approval, and plurality."
However, the truth is messier. See, the great advantage of mechanical lever machines is precisely that they do not contain computers and therefore tampering is fairly hard to do and easy to detect. (Low-tech is better, many voting advocates say, and we think with some justification...)
Now for this reason, we think many punch card machines and optical scan machines are intentionally designed not to have computers, i.e. to have counters, mechanical or electromechanical or hardwired electrical. Or if they do have computers, they are designed to be computers ultrahard to reprogram, e.g. soldered-in single chip computers with program in built-in ROM. (Perhaps somebody knows more than I do re that? Help appreciated.)
If you want to know the answers to these questions for any particular machine type, good luck. Basically, the voting machine manufacturers lie constantly and make up different stories depending who they think is listening. (Check this about how their creation of the myth of "independent testing authorities" for voting machines, and this about a lawsuit against Diebold Inc. for telling lies.) If they think the listener wants security and incredible tamperproofness, meet story number 1... So you generally cannot trust what they say. There are numerous examples of that.
For IRV, the situation is even worse still. Even if your machines have computers, and even if those computers are totally programmable, then those machines still cannot handle counting IRV votes, unless they are all connected together in a giant network, or unless just one machine has all the votes, i.e. all the ballots in the whole state are first shipped to a single central counting agency. (That is because, in IRV, one machine needs to know the totals from all the others just in order to count its own personal stash of votes. In contrast, in Range voting, a machine can total its own personal stash without knowing anything about the rest of the world.) Either way, this is asking for trouble! Think about this in an adversarial environment with people demanding recounts and tracking all votes back to their original precincts, and other bad people trying to screw up the network. IRV is an election administrator's nightmare waiting to happen.
The bottom line: We know range and approval can be handled even by machine types designed only for plurality voting, that cannot be reprogrammed, that have no computers, that are not all connected in a network, and that are located in individual precincts. Some machine types make this pleasant for the voter, other less, but all can do it. But Condorcet, Borda, and IRV cannot be handled unless there is reprogramming and in the IRV case unless there is networking or centralized counting instead of precincts (Deeper look).
That is a significant adoptability edge for range and approval and it alone should be enough to convince all serious voting-reformers to forget about Condorcet, Borda, and IRV. (Not convinced? The cost of buying new voting machines USA-wide would be of order $50 billion. The cost of buying such machines for just one typical county far exceeds the entire nationwide budgets all of the USA's "third parties" combined. Based on this monetary comparison: Who do you think has more power – voting machine stick-in-the-muds, or voting-method reformers?)