The 24 VDC Positive/Negative Fast Input Module (IC670MDL644) provides a single group of

16 discrete inputs, which may be driven by positive or negative logic.

Power Sources

The module receives power from the Bus Interface Unit to run its own 5±volt logic. An

external 24VDC supply is needed to power the input devices.

LEDs

Individual LEDs (logic side), visible through the transparent portion of the module top,

indicate the on/off status of each input. The PWR LED is on when field and backplane power

are present.
Positive or Negative Inputs

Inputs for this module can be either positive or negative inputs (all 16 inputs must be the same

type). Both types of signal produce a logic 1 (true) when the switch is closed. Selection of

positive or negative operation is made by the manner in which the external power supply is

connected to the inputs and to the I/O Terminal Block.

Positive inputs receive current from input devices and supply current to the common or negative

power bus. Input devices are connected between the positive power bus and the input terminals.

Negative inputs provide current to input devices and accept current from the common or

positive power bus. Input devices are connected between the negative power bus and the input

terminal.