There are a number of factors that affect the how many IEDs can be supported.

- The impedance of the output
- The peak to peak voltage of the output
- The input impedance of the IEDs
- The minimum input voltage of the IEDs

Tekron clocks have an impedance of 120 Ω and an output voltage of 9 (Vp-p)

The equation for calculating the maximum IEDs is as follows

**R** is the input impedance of the AM IRIG-B input of the IEDs, in ohms.

**V** is the minimum input voltage of the AM IRIG-B input of the IEDs, in volts (peak to peak).

**N** is the maximum number of IEDs.

As a note this equation does not take into account the cable resistance and assumes that all IEDs are the same.

If a 120 Ω terminating resistor is added at the end the equation changes slightly as it reduces the maximum number of IEDs

The new equation is: