Yes, it is legal for your employer to pay you at a different rate for on-call time and regular work time.
You need to be sure that if your on-call time qualifies as “work,” you are entitled to be paid at least the minimum wage for it. However, there’s no legal requirement that your employer pay you the same amount you earn when doing other types of work.
For the most case, the issue over on-call time is whether it counts as work time at all. The law depends on whether you have the right to spend the time as you see fit or whether your employer has control over your time. The more restrictions placed on your time, and the more likely you are to have to actually work during your on-call time, the more likely you are entitled to be paid.
David Payab, Esq. from The Law Offices of Payab & Associates can be reached @ (818) 918-5522 or by visiting http://payablaw.com/