When Did Baby Monitors Come Out? 1937 to 90s to Present

History of Baby Monitors

The history of baby monitors is tied to the history of radio broadcasting which developed during the first world war.  Radios were already very common in the 1920s but it took a very tragic incident in 1932 for the first audio baby monitor to be conceptualized. The Lindberg baby kidnapping incident is credited as having inspired Eugene McDonald, the president of Zenith Radio Corporation to experiment on an audio baby monitor which later became Zenith Radio Nurse.  Eugene McDonald first put together the basic microphone, speaker, and radio to listen to his daughter. When he was assured that the technology could work, he tasked a Japanese-American engineer, Isamu Noguchi to design the first baby monitor in 1937.

Newspaper snapshot

The invention of the First Baby Monitor – Zenith Radio Nurse in 1937

The Zenith Radio Corporation engaged Isamu Noguchi to design the first baby monitor in 1937. The audio baby monitor which was complete and ready for sale by 1938 was named Zenith Radio Nurse. It had a sound amplifying system with two units, the Guardian Ear and a Radio Receiver. The guardian ear’s analog intercom system transmitted sound on a 300 kHz signal transmitter over the power line. The communication was one-way.

The Zenith radio nurse first sold for $29.95 in 1938, an equivalent of $523 in 2019. This was quite expensive and in addition, its electrical transmission was plagued with technical problems, mainly distortions and RF interference. It shared a radio frequency with other consumer products, mainly car radios and garage door openers. Below is how the Zenith radio nurse worked:

1. The Guardian Ear controlled a microphone, a sound amplifier, and an oscillator circuit(modulator ).

2. The generated circuit was conducted by means of the lighting circuit and was intercepted by the radio nurse

3. The receiver unit of the Zenith Radio nurse had a detector, sound amplified, and sound reproducer.  The total amplification from the microphone to the speaker was in the order of 500,000 times. This was capable of making the slightest sound audible on the receiver.

The Zenith monitor did not work well with very loud volumes as it resulted in distortions and speaker rattles.

Following the Japanese attack on Pearl Harbor, anti-Japanese sentiments swept through America and many receivers were destroyed, making them very scarce. In fact, it is now sold as an antique and can be found in a few museums. If you are interested and want to learn more about the Zenith Radio Nurse, you can read the original Zenith Radio Manual.

The receiver of Zenith Radio Nurse (Parent unit in 1937)
The Guardian Ear/Transmitter Unit of Zenith Radio Nurse (Baby Unit in 1937)

Below is an ad/commercial that appeared in a newspaper in 1938.


Evolution of Baby Monitors:1937 to 1970

The first designed baby monitor, Zenith Radio had a one-way intercom and relied on an electrical circuit to transmit its analog audio signals


Because of the challenges discussed above, Zenith Radio Nurse model was not produced after 1938 and the few zenith nurses were bought by museums because of its unique “industrial design”.

Between 1937 and 1960s, most baby monitors in the market were sold by a few manufacturers that used Zenith’s expired patent and analog signals to transmit audio. During WW II, troops used hand-held analog radio devices to communicate and the biggest disadvantage was that only one conversation could occur at a time, on each channel. This is called the simplex mode.

The troops managed to overcome this obstacle by tuning receivers and frequencies to different frequencies but this was difficult as they were using the lower frequency bands, 27 MHz or 49 MHz. Basically, they were limited by the limited number of available frequencies. Below is a video describing analog baby monitors in the 49 MHz bands.  

Although analog radio devices were in use for a long period, they were mainly preferred because they had a better ability to communicate especially when a received signal was weak and/or noisy. 

The Invention of Frequency Hopping Spread Spectrum (1941)

The history of baby monitors is very much tied to the invention of a secure communication protocol called Frequency Hopping Spread Spectrum (FHSS). The protocol was invented in 1941 by two Americans, Hedy Lamarr and George Antheil who patented their invention of a secure security protocol that successfully enabled the Allied Forces to communicate and steer torpedoes without being noticed or intercepted.

The technology utilized a spread spectrum sequence which basically allowed signals to hop from one sub-frequency to another during transit. The spread spectrum technology was named Frequency Hoping Spread Spectrum (FHSS).

The FHSS guarantees 100% privacy of all communications and the technology is now being used by some of the best-rated baby monitors such as Infant Optics, Babysense video baby monitor, Hellobaby, and Eufy Spaceview. We have a separate post with a list of top hack-proof baby monitors using FHSS technology which you can check out.

It is, however, important to note that while FHSS technology was discovered in the 1940s when the baby monitor industry was at its nascent stages, the technology was not used in baby monitors until the 90s. First, they had to discover digital signals to replace the analog baby monitors and enable encryption for better communication security. 

The Emergence Of Digital Signals and Rise of Digital Baby Monitors

In 1965, a digital processing signal technology was discovered which paved the way for digital signals technology. 


Difference Between Analog and Digital baby Monitors


  • Analog baby monitors use analog radio signal that operates under 49 MHz frequency band
  • Analog baby monitors easily pick up noise and is prone to interference by other devices such as cordless phones which operates at a frequency close to 49 MHz (Cordless phones operate on frequencies bands between 40 and 50).
  • Analog baby monitor signal is continuous
  •  An analog baby monitor allows you to select from several channels in case the channels you’re currently utilizing has a lot of interference. Current monitors automatically scan the channels while old ones required users to manually select channels.
  • Analog baby monitor Signal does not travel long distance compared to digital baby monitors
  • The analog baby monitor signal transfer speed is significantly lower compared to a digital baby monitor.


  • Uses digital radio signal that operates under 1.9 GHz, 2.4 GHz or 5.0 GHz frequency bands. Those that operate in the 1.9 GHz are called DECT baby monitors.
  • Prone to less interference but still receives interference from devices that use the 2.4 GHz or 5.0 frequency band such as wifi routers.
  • Better quality data transferred – audio or video
  • Uniform signal reception. It has better coverage and the data does not lose its quality as the parent unit is moved away further from the baby monitor unit.
  • More signal capacity transmitted per second

Evolution of Baby Monitors:1970s, 1980s and 1990s

Baby Monitors in 1970s

1974: A patent was filed in Spain by Fernandez Aguado Rafael. The patent was for an apparatus for monitoring the intercom. It’s was described as a device to monitor young children and patients. Apart from monitoring audio, the baby monitor would allow two-way communication. This baby monitoring device would be different from the Zenith Radio Nurse in that it allowed the caregiver or the parent to communicate with the baby. It was however designed to be similar to a telephone as it had a call button and a switch and some argue that this was not entirely a baby monitor.

1979: A patent for a breath monitoring device was filed by James K. Frost in Australia and later in the US.

The device was designed to monitor the breathing of an infant and sound an alarm in case of cessation. An electromagnetic transducer was attached to a ‘cot’ or baby’s crib and it was supposed to be compressed every time a child breathes.

The transducer was attached to a microphone and it continuously produced noise if the breathing is normal. It did send an alarm in case the breathing ceased.

Baby Monitors In 1980s

1980 marked a period of great progress in baby monitors technology. Patents for transmitter units, speakers, secure cords, and receiver units were approved.


Companies such as Fisher-Price started manufacturing baby monitors as it had become a lucrative space compared to its traditional toys specialty products. Fisher-Price analog baby monitors were the best-selling baby monitor brands in the 1980s. Mattel Inc. bought out Fisher-Price in 1993.  

Safety 1st 

Another baby monitor manufacturing company that emerged in the 1980s was Safety 1st which was formed in 1984. In 1987, Safety 1st released its first baby monitor which was the best-selling brand by 1993. 

Baby Monitors In 1990s

The history of baby monitors cannot be complete without the 90s. The 1990s were marked by the emergence of several baby monitor manufacturers such as Safety 1st, a company that saw incredible success selling analog baby monitors. In addition, several patents were filed which paved the way for growth in the nascent baby monitor industry. Two factors majorly contributed to the growth of the industry: News media and FCC regulations. 

Factors that fueled the growth of the baby monitor industry in the 90s

  1. News Sites/Channels

Several TV news channels ran stories of what some cameras had revealed – mostly gross examples of caregiver misconduct when the parents were away. The shocked public began to buy the cameras, especially pinhole cameras. This fueled the development of nanny-cams, small discrete cameras which could broadcast video and audio for a range of up to about 300ft. By the early 90s, Hi-8mm video formats began to catch on. By Mids 90s, hand-held Hi-8 recorders were under $1,600 and dropped to less than $900 by 1999.

2. FCC Regulation and Baby Monitors

FCC also made several changes to regulations of audio and video transmission in the 1990s, mostly the range that signals could be transmitted and the frequency band. In 1995, FCC approved baby monitor electronic manufacturers to transmit signals in the 900 MHz frequency band and this significantly improved the audio quality as it reduced RF interference and noise. Towards the end of the 1990s, FCC also approved the transmission range of some reputable vendors to up to 3 miles. Safety 1st, one of the first manufacturers of baby monitors increased their sales by more than 50% in 1993.

Notable Baby Monitor Patents In the 1990s

The most innovative patent was the wireless baby monitoring device which operated above the 900 MHz frequency band and was capable of operation at a relatively low DC power. This baby monitor only allowed one-way communication and was powered by batteries. This baby monitor was the first one to design a truly portable parent unit but it still had antennas to receive transmitted FM radio frequency and speakers for converting the received RF signal to audio signal. The transmitting units were capable of AC or DC operation and they had a transducer for converting an audio signal – such as a baby’s cry – to an electrical signal which is processed by the transmitter circuit. Before Wilson Law invented this wireless baby monitor, all baby monitors produced in the 1970s and 1980s used the 27 MHz or the 49 MHz frequency bands. In 1995, the FCC allowed consumer electronic devices to use the 900 MHz band (between 902 and 928 MHz). The higher frequency bands were desirable because they allowed more channels resulting in less RF interference and noise. 

This baby monitor consumed a very small amount of power with DC operation. It could operate on small 1.5 V batteries and this was significantly improved as all the baby monitors in the 1970s, 1980s and early 90s used the 9.0. This innovation was submitted by Wilson Law in 1995 and was assigned to Golden Eagle Electronics Ltd.

In 1997, a baby monitor with playback and two-way communication was invented by Cynthia Altenhofen. The baby monitor allowed the caregiver or parent to record a soothing message for playback to the baby in response to activation of a play switch. This was the first baby monitor with a message storage mechanism.

The 2000s to 2015 – Rise of Video Baby Monitors

Prior to the 2000s, most baby monitors did not use wifi to transmit signals. Analog baby monitors used the analog signal while digital baby monitors started using the 2.4 GHz Wifi, DECT, or FHSS technologies to transmit audio and visual signals. It is worth mentioning here that some of the best baby monitors, the best-selling actually still use FHSS technology. Infant Optics DXR 8 and Eufy Spaceview are the two most secure baby monitors that still use the FHSS transmission technology. 

Prior to the 2000s, baby monitors with a camera unit had gained a foothold in the 90s. As discussed in this article above, news outlets including TV ran several stories of nannies that were mistreating babies when parents were away. These stories were made possible by nannycams which basically recorded a video of the baby when the parents were away. Parents had seen the need to purchase baby monitors and as prices continued to fall in the 2000s and with the emergence of wifi baby monitors, baby monitors continued to become very popular.

Because of the stories, scared parents bought the nanny cams and by the end of 1999, video baby monitors were fairly known by a good portion of American parents. Another big development in the 2000s was the use of wifi to transmit signals. The internet has contributed immensely to the growth of baby monitors. There are more than 30 patents relating to video baby monitors at present with most of them seeking to utilize the 2.4 GHz band that is used by wifi.

All these were filed within the last two decades and there are several other pending video baby monitor patents. Some of these baby monitors have had immense success with consumers. Arlo baby became one of the best-selling wifi baby monitors last year (2018) with parents being satisfied mostly with the picture and video quality. Video baby monitors are now being integrated with some of the smart home devices such as Apple Homekit, Amazon Alexa Echo, and Google Home Hub Max. Google has actually approved a list of cameras that are compatible with Google Home Hub and Arlo and Nest are some of the compatible baby monitors. 

Hacking of Baby Monitors

The first popular story of a baby monitor being hacked was reported by CNN in 2009. Since then, thousands of cases of baby monitors being hacked and this has been the biggest critique of wifi baby monitors. Hackers have had a chance to exploit loopholes and access signals over the internet. We have a separate report on baby monitor hacking which you can read if interested. 

Notable Video Baby Monitor Patents:

Successive video baby monitor patents were filed by VTech in 2003, Jollybaby in 2008, Samsung 2011, BabyTech in 2012, Panasonic in 2015. BabyTech’s patent was for car baby monitor, a space that’s yet to gain momentum. These were patents for a basic video baby monitor without wifi and no backup power. In 2007, Graco Children’s Products Inc. was assigned a patent for video baby monitors with backup power.

Home Fetal Doppler

In 2009, FDA approved the sale of a commercial home-based fetal doppler, also called doptone. One of the first approved fetal doppler was Sonoline B and C.

Some companies that have some of the best performing baby monitors such as Infant Optics did not invent their technology but bought the license to manufacture a non-wifi baby monitor that has sold over 500,000 units. Infant Optics DRX 8 had been regarded as the best baby monitor of all time.

2015 Onward – Smart Baby Monitors

Several smart baby monitor companies that utilize machine learning, sensor fusion, and artificial intelligence to measure vital signs have emerged. These baby monitors have been attributed to saving lives from SIDs, among others. They track vital signs such as breathing, blood-oxygen level, heart rate, and sleep, among others. The American Academy of Pediatrics (AAP) however cautions parents and caregivers against these smart baby monitors. In a 2018 study led by Chris Bonafide, MD, smart baby monitors were found to not have any role in preventing SIDs. The report challenges the accuracy of pulse oximetry-based baby monitors. The report tested, Owlet Smart Sock 2 and Baby Vida. (You can read the 3-page report here).

Notable Smart Baby Monitors

1. Owlet Smart Sock 3

Notable among smart baby monitors is the Owlet Smart Sock. Owlet Smart Sock is a wearable monitor that uses pulse oximetry technology to detect the baby’s pulse rate and oxygen levels. Owlet launched its Smart Sock in October 2015 and has since sold more than 250,000 units after successfully filing a patent in 2014. You can read our separate post on Owlet Smart Sock 2 and 3 here. Owlet Smart Sock 3 was just released in July 2020 and has some great features that differentiate it from the second-generation smart sock.

2. Nanit Plus

Nanit, another smart baby monitor uses computer vision to measure and track a baby’s sleep. Nanit received its patent in 2017 and it’s the first baby monitor to use computer vision and is HIPAA compliant. The company founder and CEO Assaf Glazer have some of the patents to his name, including a patent for a portable mount for a monitoring camera. They received a patent period of 15 years! Both Nanit and Owlet are expensive compared to regular baby monitors each selling for at least $300.You can read our detailed review of Nanit Plus.

3. Miku Baby Monitor

Miku is another smart baby monitor that was recently launched with breakthrough technology. Miku uses Sensor Fusion Technology. Another smart baby monitor that uses AI is Loveys Baby Monitor.

Baby Monitor Prices Coming Down

The growth of the baby monitor industry has brought several competitors and the consumers have benefited immensely from this as the prices have been coming down. Some of the best video baby monitors with great video and picture quality sell for as low as $30. In the late 1990s, the Hi-8 camera sold for about $900, and that could buy you almost 30 video baby monitors of Wyze Cam Pan, the cheapest, best-selling baby monitor of 2019. You can read more about baby monitor prices on our comprehensive analysis of price trends over the past ten years.

Frequently Asked Questions on Baby Monitor Invention

When did the first baby monitor come out?

The first baby monitor came out in 1937 following the invention by Eugene F. Mc. Donald of Zenith Corporation. Eugene developed the baby monitor but it was designed by Isamu Noguchi, a Japanese-American sculptor, and designer. It was an audio baby monitor and was called Zenith Radio Nurse.

When was Zenith Radio Nurse, the first baby monitor invented

The first baby monitor was invented in 1937 by Eugene F. McDonald and was designed by Isamu Noguchi.

Are Analog Baby Monitors Safe?

Analog baby monitors are considered safe as they emit less electromagnetic radiation when placed at least a few feet away from the baby. Digital wireless baby monitors emit microwave radiation throughout the baby’s room. However, analog baby monitors have significant interference and noise.

What is the advantage of baby monitor operating on 900 MHz frequency

They experience less radio frequency interference as they have several channels.

How were baby monitors in 1990s?

Baby monitors in the 90s had evolved significantly from those in the 70s and 80s but they still looked much like the “walkie talkies.” Some of the models that were sold include Gerry Premier 1990 Model 603. You can read more about baby monitors in the 90s in the article above.

What were some of the baby monitors in 1980s

Fisher-Price Baby Monitors were the best-selling baby monitors in the 80s

Our related articles on the history of baby gear:

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