first,be sure that your de voltage is 5v purly after loading,and also check this link for mor information www.national.com/ds/LM/LM555.pdf

both are the same only difference in the memory

i think you have have to search about the elevator aplication,i made it before.

hello guys i need your help,i'm telecom engineer,asking for some institutes in india to study gsm & cdma courses thanks