"Pin 1" Location on Headers and Receptacles

We frequently receive questions from customers asking for “pin 1” or “circuit 1” designations for receptacles and headers. Most of these designations can be found in the datasheet or spec sheet for the particular connector in question.

For example, JST’s XA series headers show the “circuit 1” location on their connectors in their datasheet:


The full datasheet for JST’s XA series connectors is here:

Additionally, many ribbon cable connectors will reference pin one on their drawings or datasheets to show the orientation of the ribbon cable. Below is an example of the pin 1 designator for CW Industries’ CSC10S-ND:


Click here to access the link to the specs for CSC10S-ND.

Non-polarized connectors typically don’t have a standard for pin 1 markings, so if there isn’t a reference to a pin 1 in the datasheet, the customer will need to decide their pinout.

If you are unsure about pin designations for connectors or need to confirm if there is any on your parts, feel free to comment below with any questions or make a post here on the forum and our technical staff will assist you.