SN74LS20
DUAL 4-INPUT NAND GATE (Motorola)
SN74LS20
Dual 4-Input Positive-NAND Gate (Texas Instruments)
SN74LS20N
DUAL 4-INPUT NAND GATE (Motorola)
SN74LS21
DUAL 4-INPUT AND GATE (Motorola)
SN74LS21
DUAL 4-INPUT POSITIVE-AND GATE (Texas Instruments)
SN74LS22
DUAL 4-INPUT NAND GATE (Motorola)
SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS (Motorola)
SN74LS221
Dual Monostable Multivibrators (ON Semiconductor)
SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS (Texas Instruments)
SN74LS2323
DUAL LINE RECEIVER (Texas Instruments)