if you work for a company that has union representation, and your contract allows it, you might get paid a contractual amount. Most government employers have some sort of pay for those called up or activated. Example- I am a county employee that is also a reservist. Activated for a year. My military pay was less than my county pay. I was paid the difference between county and militar, so that my military equaled my county. I did not get full pay for both. Every company is different.
