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Saturday, June 18, 2011

Nintendo Light Telephone (オプトエレクトロニクス 光線電話LT, 1971)

The Light Telephone must be one of the most unorthodox of Gunpei Yokoi’s ideas to make it into production (the Chiritori toy vacuum cleaner being another candidate for that title). Like the Kousenjuu light gun series, it demonstrates very creative use of light sensors.

Nintendo Light Telephone (1971)

The Light Telephone's full name is Opto-electronics Light Beam Telephone LT (オプトエレクトロニクス 光線電話LT). The "LT" (obviously) being shorthand for "Light Telephone". The kanji "光線電話" reads as "kōsen denwa".

So, if you are in a vintage toy store in Japan, ask for "oputoerekutoronikusu kōsen denwa eru ti". Chances that they will have one will be slim though, as it is pretty rare these days.

Using visible light to transport sound is immediately intriguing. However, the principal used is not novel. In fact, around ninety years earlier, Alexander Graham Bell and his assistant Charles Sumner Tainter first invented it, and called it the Photophone. With his invention, Bell created the first wireless communication.

Ten years before the release of Nintendo's Light Telephone, an American company called Infrared Industries, Inc already produced a toy based on this technology. It was called the Astro-Phone.

Astro-Phone by Infrared Industries, Inc (1961) [image by Eric Wrobbel]

The full name of this futuristic item from 1961 - labelled as "From the frontiers of science" and "Like Magic" - was Infrared Astro-Phone. It uses a regular flash-light bulb, together with a filter to block all but infrared light. This way, communication happened through intra-red light, invisible for the human eye.

The Astro-Phone had a great design [image by Eric Wrobbel]

But back to the Nintendo Light Telephone.

The sound picked up by the microphone of the Light Telephone is coded into the transmitted light, decoded again by the receiving party’s Light Telephone using a light-dependent resistor (LRD), and played over the headphone. This creates, in effect, a two-way walkie talkie without the use of radio waves.

Looking at the box art, it was pitched more as a novelty item for adults than a children's toy.

Released in 1971 with a price tag of ¥9,800, it was quite expensive and beyond the pocket money league.

The Light Telephone box is big: 55 by 38 centimeters and 13 centimeters high. All items are packed in a two-piece polystyrene foam shell with a cardboard top cover.

The set contains two 'Light Telephones', consisting of a headphone and a hand-piece with a light source, light detector and a microphone. The hand-piece design is a cross between a torch light and an 8mm film camera.

Light Telephone manual front page

Additional accessories included are two plastic "filter-caps" (フイルターキャップ) that limit side-light, and two plastic "attachment hoods" (アタッチメントフード) that further block (sun)light intervening with the reception.

Light Telephone with filter-cap attached

The instruction are fairly simple: both users plug their respective headphones in the hand-piece and aim at each other to make contact. You can speak simultaneously.

The manual explains how the Light Telephone can be used through windows and via mirrors. It can also double as a regular torch (not sure if the rabbit caught in action in the instruction below appreciates this, though).

On the right-side of the Light Telephone's hand-piece a telescope is mounted, which allows the users to take precise aim at each-other, which is necessary for the best reception (well, necessary for any reception for that matter).

A hand-strap is also available, which gives extra grip when handing the heavy (1.3 kilogram!) hand-piece.

Overall, the Light Telephone is very sturdy build, from high quality, durable plastic. A great looking metal embossed name plate is attached to its body.

The "LT" logo and Nintendo branding are added to the filter-cap.

When we take the filter-cap off, we see the plastic lens which is placed in front of the light sensor to focus the incoming light.

A detailed instruction manual is included with the Light Telephone.

Light Telephone manual

On the left-side of the Light Telephone, we see the on/off switch, the battery door and two sockets for the headphone (left) and one for an external microphone (right).

An external microphone is not really needed, as a microphone is integrated in the back of the hand-piece.

The bottom black circle is the exterior of the integrated microphone

A copyright notice (1971) is embossed on the body of the Light Telephone.

The weight of the Light Telephone is for a great part caused by the batteries. This power hungry beast requires no less than 6 batteries per hand-piece: 4 D cells for the light, and 2 AA cells for the electronics.

Now that's a battery compartment! You could park a bus in there.

The total required 12 batteries were included with each set. Nintendo clearly wasn't into this "batteries not included" stuff.

In the bottom of the hand-grip, a metal inner threaded tube is placed.

This can be used to attach it to a standard camera tripod, which allows a much steadier communication between the Light Telephones as well as use over greater distance.

When switched on, the Light Telephone projects a bright beam ahead. This is the light beam that is used to transport the sound from one Light Telephone to the other.

Under the right conditions (not too much sunlight, two sets perfectly aligned) it works surprisingly well for distances of between 10 and 30 meters.

In case of sunlight, the attachment hood can help counter some of the sound quality deterioration which occurs when there is too much environment light.

The head-phone is a basic affair, with a single speaker. The head-band is adjustable to fit various head sizes.

The black foam on the inside of the speaker cup is the only part of the Light Telephone which usually did not stand the test of time very well: after forty years this has often hardened to the point of crumbling.

The Light Telephone contained, for its time, quite elaborate electronics and expensive parts, which explains the high retail price.

The light sensor can be seen at the top of the Light Telephone (the silver component that sits above the light reflector).

It's always cool to see what's inside - have a look under the bonnet, so to speak

The light source is standard light-bulb, which can be replaced easily.

The Light Telephone is one of my favorite Nintendo items. On the one hand it is totally impractical; where walkie-talkies based on radio waves (like Nintendo's own Companion set) can be used day and night, around corners and through walls, the Light Telephone required much more optimal circumstances, in particular that the two people communicating had to be directly facing each other.

However, when you see it working you can only be amazed by the fact that it does work. And it is a lot of fun to use.

That it was released shows that Nintendo was willing to try almost anything at this point in time. And of course, great success seldom comes without any risk taking and trying something new and left-field.

It is not known exactly how well this one fared, but it certainly did not sell in significant numbers, resulting in its current rarity. It was probably a little too odd (and expensive) to garner mass appeal.

A complete Nintendo Light Telephone set

Although the Light Telephone was only sold in Japan, it did attract some attention in the foreign press, as is evident from below article taken from US publication Popular Science (issue December 1971).


  1. This is a neat concept. The article cites it as working up to a quarter-mile - ever try it at really long distances?

  2. @docmarionum1 - I never tried it at those kind of distances. I may give it a go in the near future using a tripod (haven't done that myself before) and see where its limits are.

  3. Woah! it was in popular sicence?

  4. A correction. The article reads

    "The kanji "光線電話" reads as "kōsenjū denwa". "

    Not quite. It reads as "kōsen denwa" (light-beam telephone). Not sure where you've got the "jū" from...

  5. @anonymous: you are quite right. Juu was leftover from sloppy copy-paste job. Now corrected. Thank you for pointing this out.

  6. What a cute invention. I wonder what accuracy you need when pointing the devices at each other.. surely that'll get harder with distance?

    1. I bet in pitch darkness it'd be quite effective. Aiming would be helped by the fact that, if you've got the other guy dead-on in your sights, he also has you dead-on. And a certain amount of wobble would just reduce the strength of the signal, rather than cancelling it completely.

      That's all just supposing, from what it is.

  7. So what would one expect to pay for one of these today if it was complete and in good condition?

  8. @simon - it is really hard to give a value for these kind of items. The are not offered frequently, but demand is also limited, resulting in heavily fluctuating prices.

    One just sold for ¥50.000 (US$700) on yahoo japan (, but I have also seen one sold on ebay recently for US$91, in simliar condition (!

  9. The Astro-Phone predates the Nintendo LT by 10 or 15 years! Like the LT, it is a gun-trigger talkie that communicates over a flashlight beam. The light is paired with a photocell that receives incoming light.

    The Astro-Phone was made by Infrared Industries in Waltham MA and was marketed in the US during the late 1950s. It is housed in an even more stylish case.

    For more info, or general enthusiast discussion, use the contact form in my blog, awildduck (d0t) com.

    1. That Astro-Phone looks very interesting. I like its tag-line: "from the frontiers of science". Thanks for sharing the information.

    2. I have just update the post with a mention of the Astro-Phone. Thanks again for bringing this to my attention.

  10. I received a message from a reader called James, with some additional information on this topic:

    I would like to add comments about the AstroPhone. You suggested that it did not use infrared light because it used an ordinary flashlight bulb. Please allow me to bring to your attention that the WWII German military communications device (Lichtsprecher) is reported to have used a standard bulb with an optional infrared filter when covert communication was needed. Also, Chris Long, an Australian light communications experimenter, reported that in his experiments from 1971, the light bulb he used could be biased so low that there was no visible glow, and audio could still be sent through his system.

    I feel there are two real issue of using a light bulb. One of efficiency - most of the energy into an incandescent bulb leaves as heat, conducted or radiated away in a form not useful to the detector used at the receiving end. The other is frequency response - while the electricity used to drive the bulb has no practical limitations at audio frequencies, the filament that converts electricity into heat and light cannot heat up or more importantly cool off fast enough for the emitted light ( both visible and infrared ) to match the frequency response of the applied signal. As a result the audio quality is heavy on the bass and light on the treble.

    For what it is worth, light communications experimentation with red LED for the light source was conducted over a 173 mile distance in Utah in October 2007. Clint Turner, amateur radio call KA7OEI has the details on

    1. Thanks for the information James! I have updated the post accordingly.

  11. Replace regular ratty torch bulb with a high-brightness / much faster reacting LED equivalent, swap those ancient low tech D-cells for a couple of cellphone spec lithium batteries, and fit a couple of cantenna-style pringles tube gun-hoods around both light and receiver, and you could probably transmit for miles with this thing, at night, having carefully aligned the two units in daylight, on tripods and such.

    With rather higher audio quality (indeed, probably enough to transmit data or low grade digital video, even), and no need for either expensive and easily damaged/tapped cables, even pricier fibre, or easily-intercepted radio broadcast. Abusing ancient novelty gadgets for secure communications a go-go!

    (Even better if you could use it to modulate the output of a laser somehow, but then you'd likely have to modify the reciever as well...)

  12. I am very nostalgic.
    I was born in 1960.
    I remember that I really wanted to see this ad when I was a kid.
    It is a good memory now.