The select (SELx) pins are logic pins that control the connection between the source (SxA, SxB) and drain (Dx) pins of the TMUX113x devices. When a source pin is not selected that pin is in an open state (HI-Z). When a source pin is selected the switch conducts to drain. The logic control pins can be as high as 5.5 V.
When the EN pin of the TMUX1133 is pulled low the SELx logic control inputs determine which source input is selected. When the EN pin is pulled high, all of the switches are in an open state regardless of the state of the SELx logic control inputs. The TMUX1134 SELx logic control inputs determine which source pin is connected to the drain pin for each channel.
The TMUX113x devices can be operated without any external components except for the supply decoupling capacitors. Unused logic control pins must be tied to GND or VDD in order to ensure the device does not consume additional current as highlighted in Implications of Slow or Floating CMOS Inputs. Unused signal path inputs (SxA, SxB or Dx) should be connected to GND.