Eurocard

Eurocard is a European standard format for PCBs, which can be plugged into a standardized subrack. The subrack consists of a series of slotted card guides on the top and bottom, into which the cards are slid so they stand on end, like books on a shelf. At the "back" of each card are one or more DIN 41612 connectors, which plug into mating connectors on a backplane in the rear of the subrack.

The format does not define specific connectors to be used nor the signals that are assigned to connector contacts.

The format is in widespread use in many industries,.

Dimensions
The Eurocard height is specified in U (for rack unit), with 1 U being 1.75 inches. In practice heights are commonly 3U or 6U.

Eurocards come in depths that start at 100 mm and then increase in 60 mm increments. The 160 millimetres depth is the most common today, followed by 220 mm. However standard hardware is available to accommodate depths from 100 mm to 400 mm.

A single size eurocard is 100 mm x 160 mm (3U) and double size eurocard is 233.35mm x 160 mm (6U). The extra 33.35mm allows two 3U Eurocards to be supported properly next to one 6U high, with the width taken up by a card guide between the two 3U cards.

EuroCard uses 2.5mm mounting screws.

As the basis of the Eurorack format
In the late 1970s before Eurorack, there were a few synthesizer systems based on the industrial Eurocard frames: By the late 1980s, these had all ceased production.
 * Elektor Formant - 3u or 6u x 7HP, 3.5mm jacks, 31 pin bus, +/-15v
 * BME PM10 and Axiom - 3u x 8HP, phono/rca jacks, 31 pin bus, +/-15v
 * Synton 3000 - 3u x 8HP, 4mm banana jacks, +/-15v, similar format but constructed more like a modern Eurorack synth.

Dieter Döpfer built some Formant modules before producing his own systems. His polyphonic non-patchable Voice Modular System (VMS) from the early 1980s was a Eurocard based modular synth.