Unknown TI logic series

[Christian Corti]

Hi everyone,

  we've had a look inside our IME 122 calculator and discovered that it is 
full of SN14xx logic ICs. They are mainly from TI, but there are also some 
from Motorola and others. It seems that they have the same function and 
pinout as the SN74xx parts but there must be a difference since the 
machine has quite a lot of SN1401 (the SN7401 is a quad open-collector 
NAND), but there are no pullup resistors anywhere!
  Some of the types are SN1400, SN1401, SN1474, SN1490; the ALU is made up
of SN1482 and SN1483.
  Anyone knows this series? BTW the supply voltage is 5V.

Christian