RFID reader's frequencies 125KHz vs 13,56MHz

Which one do I need choose?

I have cards that can be read by RFID reader 13,56MHz, but I do not know if I make system with 125KHz then this cards can be read by this RFID?

I know that this card can be read by 13,56 MHz RFID reader!!!

May be 125 MHz RFID reader can do it too? I want this frequency because I see many readers with this frequency... and price of them it lower.

I know that I can put several cards together to RFID reader of turnstile and he can read card that he need!!!!! it means that cards reader is 13,56MHz??? HF ??

So some guys on IRC tell me that 125KHz reader can not read 13,56MHz cards!!!!

I dont know if you have solved your issue but you are right you need to have the correct reader paired with the rfid transponder(tag)

Its not just enough to know the frequency of the tags, you need to know the protocol that it supports also.

For example a 15693 reader cannot necessarily read 14443 tags.