The Gakken Denshi EX System is a series of electronic learning kits sold in Japan from 1976 to 1979 in which the components are placed in small building blocks with contacts along the outside.

The EX Series is actually the forth version of the product line dating back as far as 1965.

The first series of kits were more like the 200inOne/300inone style kits but were expensive for the time.

The Second edition and one that used building blocks came out in 1966 called the DR-1A which was slimmed down to make 16 projects followed by the DR-IIA which could make 30 projects and the DR-4A that could make 120 projects.

After the DR Seres came the SR Series in 1968 which instead of the contacts along the side came with connections on the bottom that plugged into the baseboard more akin to automotive relays.

The oridginal EX series started with the EX-15 and went up to the EX-150.

The SR range consisted of the following versions:

• SR-1A  that taught 16 projects,
• SR-2A  that taught 30  projects,
• SR-3A  that taught 100 projects,
• SR-4A  that taught 105 projects,

In 1971 the Inventer went into partnership with the Gakken company who produced the "My Kit" series and the ST Line was expanded with the following versions:

• ST-25 that taught 25 projects,
• ST-45  that taught 45 projects,
• ST-100 that taught 100 projects,
• ST-155  that taught 155 projects,

The ST range came with the familure Spring contacts on the sides and came in clear blocks allowing components to be viewed inside.

In 1973 Sales started to drop so a new series was developed. In 1976 The EX range consisted of seven versions as follows:

• EX-15 that taught 15 projects,
• EX-30 that taught 30 projects,
• EX-60 that taught 60 projects,
• EX-100 that taught 100 projects,
• EX-120 that taught 120 projects,
• EX-150 that taught 150 projects.
• EX-181 that taught 181 projects.

Unlike the previous version, the tuner/antenna module was incorporated into the new base frame along with addition modules like an IC amp, a panel meter and a light sensor.

At the time expansion kits were available that allowed the kits to upgraded to the next level version.

In 1979 the EX-181 came out wich made use of a digital synthsiser module built around the SN76477 sound generator kit.

The kits continued to be released up untill 1986 when the famicom came out and interest started to fade.

In 1991 to additional kits came out called the FX-145 which included a digital clock/FM radio module and the FX-165 which came out with a 4Bit computer module designed to regenerate interest in the kits but the damage had already been done due to the electronic games market.

In 2009's  volume 24 isuse of Otona no Kagaku (Adault Science) magazine the 4 bit computer was reproduced as a kit that ran on 4.5V (3XAA batteries).

In 2011's volume 32 issue of Otona no Kagaku (Adault Science) magazine came out with an EX-mini that taught 50+ projects but unlike the previous EX series, ran on 4.5V (3XAAA batteries) instead of the oridginal 6V (4XAA Batteries).

in 2001 a reproduction versions of the EX150 known as the EX-150 reprint edition was sold later using modern components like LEDs instead of the oridginal filament bulb but the change of components meant that the new versions were not fully usable with the old kits.

To make up for this difference and new optical expansion was released for the new revision that included an RGB LED and a 555 timer. that was available as a 60 project expansion or in the EX-210 Dulux edition.

Referances for this article is Peter vis website -  Peter Vis

And Volumes24 and  32 of Otona no Kagaku (Adault Science).