Baby Monitors

Baby Monitor Tech: FHSS, DSSS and DECT

Ashley Davis

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FHSS, DECT, and DSSS are all digital baby monitoring technologies but each technology has distinct characteristics and advantages that I have explained in detail below.

Frequency Hopping Spread Spectrum (FHSS) is the only transmission technology used in baby monitors to power secure signal data transmission. As a local closed-circuit network, it is designed to operate within 2.4 GHz frequency, which is one of the most commonly used frequencies for wireless devices.

In this guide, we will explore the basics of FHSS transmission technology, its benefits and limitations, and how it is used in baby monitors.

What is FHSS Transmission:

FHSS is a method of transmitting data by continuously hoping among multiple channels within a specific frequency band. This is done to minimize the risk of interference and enhance security.

The transmitter and receiver are synchronized to switch between these channels, making it difficult for unauthorized parties to intercept or jam the signal. This makes FHSS an ideal technology for secure and reliable data transmission, especially in environments with high levels of wireless activity.

There are two types of FHSS transmission technologies, fast and slow. Fast FHSS rapidly hops between channels within the frequency band, while slow FHSS switches channels at a slower rate. Both types offer the same level of security but differ in their speed and bandwidth usage.

FHSS technology dates its history back to World War 2 when it was used as a secret communication system that guided arms to the target without being detected or intercepted by the enemy.

The technology was patented in 1941 by Markey Hedy Kiesler and Antheil George and the technology allowed the sender to transmit audio signals in a pseudo-random pattern utilizing 88 different sub-frequencies. Some sources claim that a German physicist and electrical engineer Jonathan Zenneck had discovered it earlier and had mentioned the concept in print in 1908.

There have been two variations of FHSS technologies utilized in baby monitors, the FHSS 1.0 and FHSS 2.0. Our best FHSS baby monitor which utilizes the latest FHSS 2.0 technology with superior data encryption is Infant Optics DXR 8 Pro and is the safest.

A New Dawn in the 80s for FHSS technology:

In the late 1980s, the Federal Communication Commission (FCC) made a significant decision by permitting unlicensed usage of the 2.4 GHz frequency band, as outlined in the Part-15 regulations. This regulatory change allowed electronics manufacturers to operate in the 2.4 GHz band without the need for a special license. Consequently, this frequency band gained immense popularity among electronics manufacturers.

However, with the increasing number of devices utilizing the 2.4 GHz band, interference became a prevalent issue. It wasn’t until the FCC granted permission to select manufacturers interested in implementing spread spectrum technology that device-to-device interference began to diminish.

Overall, the FCC’s decision to allow unlicensed use of the 2.4 GHz frequency band revolutionized the electronics industry while addressing the challenges of interference through innovative technological solutions.

Advantages/Benefits of FHSS Transmission Monitors:

  • The security benefits of FHSS are a key advantage. With high levels of frequency hopping, unauthorized parties have difficulty intercepting making it difficult to hack. Our top-ranking non Wi-Fi monitor which uses FHSS also encrypts its signals on top of the first layer or default FHSS encryption making it super secure!
  • No jamming: The frequency-hopping pattern makes it challenging to jam the signal because it is difficult to determine which channel the data is being transmitted on.
  • Coexistence with other wireless systems: Since FHSS rapidly switches between channels, it can operate alongside other wireless systems without causing interference with other 2.4 GHz devices
  • Narrowband: FHSS signals exhibit exceptional resistance to narrowband interference due to their ability to hop across different frequency bands.

Challenges of FHSS Technology in Monitoring Systems:

  • Synchronization: For the sender and receiver to successfully communicate using FHSS, they must be synchronized. If the synchronization is not precise, it can lead to data loss and errors.
  • Channel interference: In dense wireless environments, there may be interferences from other FHSS systems or non-FHSS devices that could impact the quality of transmission.
  • Limited range: FHSS technology has a limited range as it uses lower power output compared to other wireless technologies like Wi-Fi. It is suitable for short-range communication.
  • Complexity: Implementing FHSS technology can be complex and require specialized equipment, making it more expensive than other wireless technologies.

Other Uses of FHSS Technology:

  • Military communications: One of the main uses of FHSS technology is in military communications due to its high level of security. The signal hopping makes it challenging for enemies to intercept and decode transmissions.
  • Wireless LANs: FHSS technology is used in wireless LANs, providing secure communication with minimal interference from other devices in the same frequency range.
  • Medical applications: Due to its resistance to interference and high security, FHSS technology is used in medical applications such as remote patient monitoring and wireless medical devices.
  • Industrial and home applications: FHSS technology is used in industrial automation and control systems, providing reliable and secure communication for critical operations. Some baby monitors we review here at SaferForBaby utilize FHSS.

Explanation of FHSS Technology.

The video below explains how the FHSS technology works and how it can be utilized by FHSS baby monitors.

What are FHSS transmission baby monitors?

FHSS transmission baby monitors are a type of wireless baby monitor that uses Frequency-Hopping Spread Spectrum (FHSS) technology to transmit audio and video signals between the parent unit and the baby unit. This technology works by rapidly switching between multiple frequency channels, making it difficult for unauthorized users to intercept or interfere with the transmission.

One of the main advantages of FHSS transmission baby monitors is their high level of security. Since the frequency channel changes frequently, it makes it challenging for hackers or other unauthorized users to access the signal and listen in on conversations or view video footage.

Additionally, FHSS technology also offers a strong resistance to interference from other electronic devices operating on the same 2.4 GHz frequency range. This makes FHSS transmission baby monitors ideal for use in homes with multiple electronic devices, as well as in busy environments such as apartment buildings or densely populated areas. This limited interference is the advantage FHSS has over DECT but is considerably lacking when compared to DSSS.

FHSS transmission baby monitors also offer reliable and stable communication between the parent unit and the baby unit. This is crucial for parents who rely on their baby monitor to keep an eye on their child while they are sleeping or playing in another room.

However, it’s important to note that while FHSS technology provides a high level of security and interference resistance, it is not completely hackproof. Skilled hackers may still be able to intercept and decode the transmission, although this is significantly more challenging compared to DECT and DSSS types of baby monitors.

DECT: Digital Enhanced Cordless Telecommunications

Another popular technology used in baby monitors is DECT, which operates on a different frequency band than FHSS technology which operates in the 2.4 GHz frequency.

DECT baby monitors operate on the 1.9 GHz frequency range and use digital encryption to secure communication between the parent unit and the baby unit. The key advantage of DECT over FHSS is that it has a longer range of transmission of up to 50 meters indoors and up to 300 meters outdoors compared to FHSS which does not exceed 30 meters indoors and around 120 meters outdoors.

DECT’s standard encryption is 64-bit while the minimum standard encryption for FHSS is 128-bit making FHSS much more secure. You should, however, note that when using the DECT repeater, encryption is no longer in place. On the other hand, DSSS monitors can use up to the highest encryption standard of 256-bit.

DECT are mostly used in cordless phones and have been adapted for use in baby monitors due to their reliable and secure communication.

However, it’s important to note that DECT technology is also not immune to hacking. In 2008, a team of researchers discovered vulnerabilities in certain DECT devices.

While encryption is included in the DECT standard, it can still be easily bypassed. This allows rogue devices to impersonate legitimate ones, as reported by Heise Security. It is possible that all DECT devices now have more secure encryption and are no longer vulnerable. It is, however, clear that DECT security settings are not at par with FHSS’s settings.

FHSS Vs. DECT Baby Monitors

Below are some other differences between the two technologies, FHSS and DECT:

Feature FHSS Baby Monitors DECT Baby Monitors
Frequency Band 2.4 GHz 1.9GHz
Spread Spectrum Yes Yes
Wi-fi No No
Licensed to Several range of devices Radios/Telecoms
Discovered in America Europe
Formerly called N/A Digital European Cordless
Encryption 128 or 256-bit 64-bit
Example of baby monitor Infant Optics DXR 8, Eufy Spaceview, Motorola MBP36XL Panasonic long range baby monitors,

DSSS: Direct Sequence Spread Spectrum

DSSS, an acronym for Direct Sequence Spread Spectrum, is a technology that builds upon FHSS (Frequency Hopping Spread Spectrum). Unlike FHSS, which hops between frequencies and sends data in bits, DSSS transmitters transmit data at once across an entire spectrum of frequencies.

DSSS has a few advantages over FHSS.DSSS revolutionized transmission by utilizing bulk transfer with data broken into bits. Instead of transmitting one bit at a time, DSSS breaks down each bit into smaller, more manageable chunks. These chunks are then processed by an algorithm to determine their values. Once transformed into wireless bits, they are transmitted across the airwaves.

Upon reception, a receiver captures these bits and uses a corresponding algorithm to convert them back into the original data. This innovative approach not only improves the efficiency of data transmission but also ensures the integrity of the transmitted information.

Here is the key difference between FHSS and DSSS. DSSS and FHSS differ primarily in their approach to frequency hopping during data transmission. FHSS hops between frequencies while transmitting data, whereas DSSS simultaneously sends data on every frequency within the designated spectrum at once.

Although DSSS incorporates built-in parity, it lacks superior resilience. Interestingly, FHSS demonstrates greater resilience compared to DSSS. In highly noisy and congested environments, FHSS outperforms DSSS-encoded baby monitor signals, highlighting its superior capability.

Similar to FHSS, DSSS uses the 2.4 GHz frequency but can also switch to the more recent 5 GHz frequency band.


Does Bluetooth use FHSS too?

Bluetooth utilizes FHSS, while Wireless USB, 802.11b/g/a (commonly known as Wi-Fi), and 802.15.4 ( ZigBee) employ DSSS. All of these technologies operate within the globally available ISM frequency band (2.400-2.483 GHz). ISM is an abbreviation for Industrial, Scientific, and Medical, referring to the frequencies reserved for non-communication purposes

Is DSSS same as Wi-Fi?

No, DSSS is not the same as Wi-Fi. Wi-Fi is a type of wireless technology that uses DSSS or other modulation techniques, depending on the specific standard being used. For example, 802.11b/g/a Wi-Fi utilizes DSSS while newer standards such as 802.11n and 802.11ac use different methods such as OFDM (Orthogonal Frequency Division Multiplexing).

Why is FHSS more secure than DSSS?

FHSS is considered more secure than DSSS due to its frequency hopping mechanism. By constantly changing frequencies during data transmission, it makes it difficult for eavesdroppers to intercept and decipher the information being transmitted. Additionally, since FHSS only transmits small amounts of data at each frequency, it is more difficult for attackers to capture and decrypt the entire message.

Can FHSS be hacked?

While FHSS is generally considered more secure than DSSS, it is not completely hack-proof. With advanced technology and techniques, and close physical proximity to the FHSS device, hackers can intercept and decode FHSS transmissions. However, compared to DSSS which is more susceptible to hacking due to poor encryption, FHSS offers an extra layer of security that makes it a preferred choice for applications where data privacy and security are crucial.

What are the differences between OFDM and DSSS?

OFDM (Orthogonal Frequency Division Multiplexing) and DSSS (Direct Sequence Spread Spectrum) are both modulation techniques used in wireless communication. OFDM is used in newer standards of Wi-Fi such as 802.11n and 802.11ac, while DSSS is utilized in older standards like 802.11b/g/a.

The main difference between OFDM and DSSS is the way they transmit data. DSSS spreads data over a larger bandwidth by using a specific code, making it easier to intercept and decipher. On the other hand, OFDM divides data into smaller sub-channels and transmits them simultaneously at different frequencies, increasing the overall throughput and making it more difficult for attackers to hack.

Additionally, OFDM uses complex coding and modulation techniques to provide an extra layer of security.

Why is FHSS a better choice for certain applications?

While DSSS can offer higher data rates, FHSS is preferred for applications where data security is crucial. For example, military communication systems or medical devices that transmit sensitive information require high levels of encryption and protection against hacking. In such cases, FHSS is a better choice due to its frequency-hopping mechanism and stronger encryption.

Moreover, FHSS offers better resistance to interference since it constantly changes frequencies, making it difficult for interfering signals to disrupt the transmission. This makes it suitable for crowded environments with multiple wireless devices.