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Digital Modulation

What is “the best” underground fence?  FM, AM or Digital Modulation?

Hidden underground fences (often referred to generically as “invisible fences”*) use radio signals. There are only two types of radio signals used for electronic underground fences:

  • DogWatch uses a digital FM signal (Frequency Modulation)
  • All other underground fences use a digital AM signal (Amplitude Modulation)

Digital Modulation (DM) is not a type of radio signal. It is a signal processing technology used to send/receive both FM and AM radio waves. Digital Modulation is used in almost all communication devices – everything from cell phones to Hidden Fences. All underground fences use Digital Modulation.


The Real Difference in Hidden Underground Fences is FM vs AM

What’s the difference? FM radio signals are ‘cleaner’ and more secure than AM signals. A good example is FM radio stations (no static) compared to AM radio stations (lots of static). That is the reason that fire/police and emergency responders typically communicate over FM channels

A simple explanation of the difference between FM and AM signals is:

  • FM frequencies use a “continuous” radio signal.
  • AM frequencies switch “on” and “off” during transmission.

Because the FM signal is “continuous”, FM frequencies are less susceptible to interference from other signals, so the fence collar is less likely to activate in unexpected locations. This makes FM systems safer for your pet.

When the AM signal is “off”, it is open to interference from other AM radio signals, such as those that come from common household electronic devices. From a hidden fence perspective, this is important because these random signals may trigger the fence collar. When the collar activates where it is not expected, it can confuse (and frighten) your pet.

Our patented SafeLink® FM signal makes DogWatch® Hidden Fences the SAFEST system for your pet.

All hidden underground fences use Digital Modulation (DM). Only DogWatch uses an FM signal.

*DogWatch hidden dog fences are often mistakenly referred to generically as “invisible fences” or “invisible dog fences.”
Invisible Fence® and Invisible Fencing® are Brand names, products and registered trademarks of Radio Systems, Inc.