On the Noma timer Mod 49550/tm151p how can you tell when the switch is on

1) Noma is old Intermatic brand name used by companies today to brand their timer.

2) Noma is usually associated with Woods timers.

3) Woods numbers also frequently start with 495 and with TM.
For example Woods has 49588 49556 and 78 84 29 28 62 57 33 53 65 44 68 32 77, but 49550 does not show

4) It is likely that you have a Woods brand timer.

5) Add a comment with in-focus photograph of timer for possible identification
http://www.fixya.com/support/r6568559-post_photograph_fixya_questions_answers

6) Open following link to possibly identify timer, and then add a comment saying which timer is same-similar to yours.
http://waterheatertimer.org/Woods-timers-and-manuals.html
Read troubleshoot section to see if your answer is there:
http://waterheatertimer.org/Woods-timers-and-manuals.html#troubleshoot