The Manual for Uniform Traffic Control Devices (MUTCD), and the California equivalent, are standards for the design and placement of traffic control signs. They have the force of law for any federal or state funded roadways, but there is no enforcement mechanism, so signs that do not meet these standards can certainly be found, both in places that just decide they know better, and in places where the public right-of-way and use is evolving rapidly and the glacial pace approval of new signs is not keeping up.
The MUTCD has 14 signs related to the use of beg buttons to cross the street, in the R10-1 through R10-4 series. One of these is shown below, the most complicated one, R10-3e. Of the 14, none offer any information about whether the beg button is required or not. This is not an oversight; it is a direct expression of traffic engineer’s disdain for pedestrians. California could, of course, add other signs with better information, after approval by FHWA, but it has not seen fit to do so.

Noting the lack of good signs that actually address real-world situations, some entities have designed their own. One example is below, which came via Don Kostelec, of whom I’ll have more to say shortly. (original source not known)

Why is the distinction between these two types of signs important? Buttons can be used by limited vision or blind people to trigger the pedestrian signal, and the auditory and sometimes vibratory message that goes with it. When the conversation started about removing beg buttons, many disability advocates were up in arms, understandably. If there is no button, there is no message.
Except, of course, for automatic detection of pedestrians, and even pedestrians types, that many other countries and a very few places in the US are installing. Traffic engineers routinely resist automatic detection as “too expensive and not practical” despite spending much larger sums on vehicle detection. Which in the case of bicyclists, often doesn’t work anyway.
Traffic engineers also frequently place buttons in places where people with disabilities, as well as everyone, can’t find them and/or can’t reach them.
So, is there a way to preserve the function of buttons needed by disabled people, while not discriminating against all pedestrians? You bet. Just label the button for its function. And put it in an accessible location.
So, Don Kostelec. He is one of my heroes, as he has done a better job than anyone I know of documenting the failures of transportation agencies to install safe and usable pedestrian facilities. Sidewalks too narrow, or that end where you really need them; ADA ramps to nowhere; crosswalks that can’t be safely used; and on and on. I highly encourage you to check out his blog (http://www.kostelecplanning.com/blog/) and Twitter feed (@KostelecPlan). He does not hesitate to call out road and traffic engineers for their failure to think, and for their failure to follow their professional code of ethics. Though he didn’t originate it, I think he is responsible for popularizing the expression “Hold my beer!” in the transportation world, implying that only an engineer drinking beer, and momentarily designing a roadway or facility before going back to drinking, could have done something that stupid.
And on this topic of beg buttons, I particularly encourage you to read his recent post, Push buttons: The good, the beg, and the ugly.
There has also been a lot of discussion about whether it is hard to change the buttons from required to not required, which is called auto recall, or just recall. A number of cities have changed hundreds of buttons in very short order because they prioritized it. Newer signal control boxes allow changes to be made remotely, changing the function and timing of pedestrian signals. Older control boxes may require that someone go out and physically change them. The older boxes are sometimes derisively called squirrel cages because they had large physical clocks with rotating dial, with pegs to change the signal on or off, as it came around. They made noises like a squirrel or hamster cage. A few idiots have been saying that pedestrian signals should not be changed remotely because of security issues. That is the whole point of modern signal controllers, part of Integrated Traffic Systems (ITS), that they can be can sense and respond to actual traffic, and can be adjusted remotely to respond to changing conditions and for changing flow when crashes occur.
There is also the issue that many transportation agencies don’t know what is at the intersection. Does it have pedestrian signals or not? Does it have pedestrian countdown or not? What is the timing of the pedestrian phase, in terms of countdown? Is the beg button required or not? They simply don’t know. Locally, Sacramento County is the worst on this issue.
Previous post on beg buttons: Don’t touch that button! Then, there are locations where pedestrian crossing is simply prohibited, for reasons having everything to do with speeding traffic and nothing to do with pedestrian safety: and crossing prohibitions, and no-ped-crossing in the grid.