7.1 Signals
How a module declares what each port carries, and the rules every patch jack follows whatever it carries.
| Clause | Applies to | Covers |
|---|---|---|
| 7.2 Signal classes | Every module with a patch jack | The seven signal classes, AUDIO, CV, VIDEO, PITCH, GATE, TRIG, and CLOCK, and their ranges |
| 7.3 Video signals | Every module with a patch jack | VIDEO on patch jacks: levels, impedances, path kinds, and bandwidth |
| 8.2 Video on 75 Ω coaxial jacks (VID-75) | A product that has it | The 75 Ω coaxial interface: the video sync ports COAX-IN, COAX-OUT, COAX-THRU, the video sync tree, and the coaxial cable |
| 8.3 Video timing | A product that has it | The formats a video sync port lists |
| Annex C | Informative | Names for ports that are not patch jacks |
Port list
A module shall publish a port list naming, for every port, its signal class or unclassified, and for a video sync port its mode (8.2) (SIG-001). A module with no ports publishes an empty list. The port list goes in the manual, on the product page, or in a claim file. For each port it gives:
- its direction: in, out, or in_out for a port that is both, such as a bidirectional expander link;
- its class, or
unclassified; - the range it claims, when that is not the class default (7.2);
- for a COAX-IN or COAX-OUT, the formats it locks to or generates (8.3).
A port that claims a class meets that class's limits, in 7.2, and VIDEO's interface in 7.3.
A port that is neither a patch jack nor a video sync port, such as a coaxial picture jack, a line audio port, or MIDI, is listed as unclassified or by its Annex C class. EIS places no requirement on it beyond what this clause says of every jack. Its class is no patch class (7.2). EIS recommends that a 3.5 mm audio socket on the panel withstand a mono patch plug (patch safety).
EIS recommends labeling each port with its class, on the panel or in the manual.
Patch safety
These requirements apply to every patch jack on a module, whatever its class:
- A patch input shall withstand ±12 V indefinitely (SIG-002).
- A patch output shall withstand an indefinite short to 0 V or to another patch output (SIG-003).
- A patch output shall not drive the patch tip beyond ±12 V (SIG-004).
The ±12 V is the rails' nominal figure, applied from a source of 1 kΩ or less. A supply's 10 % start-up overshoot (SUP-006) is a rail figure: no conforming output drives a tip beyond ±12 V while its rails are anywhere inside the supply's limits.
EIS recommends:
- that a patch input withstand ±15 V, the rails of the ±15 V systems a patch cable can reach through an adapter;
- that every other 3.5 mm socket on the panel, such as a TRS MIDI, headphone, or stereo port, withstand ±12 V on its tip and a short from tip to sleeve, since a mono patch plug fits it;
- that every patch jack, and every RCA, BNC, or SMA jack, have its sleeve or shell insulated from the panel metal, so that no signal return runs through the panel and the case; 5.2.1 gives the construction on FR4 and on metal.
Patched signals only
A patch jack shall carry patched signals only: a module shall neither take nor give its video sync at a patch jack, and no patch jack shall list a format of clause 8.3 (SIG-015). The video sync is system configuration, wired once behind the panel at the video sync ports of 8.2, so patching never changes a module's timing. A timing pulse on a patch jack is a patched signal like any other (7.3).
A product that generates or locks to an external video sync shall take or give it at a video sync port on its rear (SIG-018), a COAX-IN or COAX-OUT of 8.2; a product with no such port neither generates nor locks to one.
Jacks inside the case
A jack inside the case shall not be a BNC jack: none at the rear of a module, on a bus board, or on a power supply (SIG-017). A BNC jack is on the outside of the case only, on a front panel or an enclosure's wall. A coaxial jack inside the case is an RCA, mated with a push, or an SMA, mated with a few turns of a small nut: a BNC's body and bayonet sleeve need room for fingers to grip and turn, which the space behind the panels and over a bus board does not give.