Electricity is universal, but hardware often varies by country. In this post I’ll outline the various types of pilot switches and how they work here in Japan. You should note that here a “pilot switch” refers to a distinct type of LED embedded switch (see below for details). There are broadly 5 types of these LED embedded switches, commonly referred to elsewhere as pilot switches.
1. Hotaru; technically known as ijitentou
2. Pilot; technically known as doujitentou
5. 24/7 Pilot; technically known as joujitentou
1. Hotaru; ijitentou (ほたるスイッチ； 異時点灯). Hotaru is the Japanese word for “firefly”, and is the type that lights up when the switch is OFF, and turns off when the switch is ON. This is useful when the area is dark, making the initial location of the switch difficult otherwise. Wiring is the same as an ordinary single-pole switch.
Ijitentou translates literally to “alternative illumination”, referring to the inverse relationship between switch and lamp.
Be mindful that LED lights should not be used with hotaru switches due to the small current that passes through the hotaru (to light it up) when the switch is off. Contrary to incandescent bulbs, LED bulbs are sensitive enough to pick up on this small current and will flicker when the switch is off.
2. Pilot; doujitentou (パイロットスイッチ； 同時点灯). This type is the opposite of the hotaru, and lights up when the switch is ON, and turns off when the switch is OFF. It essentially mirrors the on/off of the resistor it’s controlling, and is used to highlight the ON status (as opposed to its OFF status) of an appliance that might be located in a place that isn’t visible from the switch. Wiring is the same as an ordinary single-pole switch.
Doujitentou literally translates to “simultaneous illumination” – for obvious reasons.
Pilot switches have specified ampere ratings such as 0.5, 4A, or 15A. It goes without saying that you must choose the switch that matches the appliance in question. For example, a 0.5A switch can be used for a 1 to 50 watt appliance, and a 4A switch can be used for a 10 to 400 watt appliance. 15A pilot switches are available as well, but they come as a 3-way (single pole, double throw) that can double as single-pole, and can be used for 60 to 1500 watt appliances. If your needs require a wider range, use the hikaru switch (see below).
3. Hikaru switch (ひかるスイッチ). This one is basically a glorified version of the ordinary pilot switch. It doesn’t have the range-limitations that the pilot switch has, but requires 3 wires instead of 2. It will light up regardless of the wattage of the appliance. This one’s useful for appliances with very small and/or large loads.
Just be mindful when wiring, and confirm that you in fact have a Hikaru switch, and not a pilot switch. Connecting a pilot switch with 3 wires as in the diagram above will result in a short.
4. Pilot/Hotaru (パイロットほたるスイッチ). A sweet little hybrid that has ‘all of the above’. This one will light up red when the switch is ON, and light up green when OFF. A bit of an overkill if you ask me, but who doesn’t like a dash of overkill from time to time. Just don’t get confused with the colors, as green implies “go”, and can be subconsciously taken as ON. Of course, presumably from the manufacturers point of view, red can be taken as “in operation”, and green as “cooling off”, or something to that effect.
5. 24/7 Pilot; joujitentou (常時点灯スイッチ). This one is just ON 24/7, and used basically as a little lamp to illuminate the switch. This kind of pilot switch is generally only necessary for dim rooms with little or no lighting ever, or older folks with bad eyesight, as it takes up that much more space in your switch box.
It is also rarely seen today, as the more modern pilot/hotaru switches perform this same function with superior efficiency and design. In other words, it’s safe to think of it as obsolete.
Joujitentou translates literally to “ordinary illumination”, in this case ordinary referring to the lamp’s continuous state of illumination.
Within these 5 individual switch types, there are further subdivisions made distinct by suffixes B, C, D, and E.
B: the standard single-pole, single-throw switch.
C: 3-way switch that can be used to toggle between 2 switch-locations.
D: double-pole, double-throw switch, used to switch 2 parallel signals simultaneously; recommended for 200V appliances.
E: 4-way switch, used in between 2 3-way switches for 3 or more switch-locations.