> For the complete documentation index, see [llms.txt](https://docs.ceruleansonar.com/c/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ceruleansonar.com/c/ethernet-rov-locator/connecting-and-powering-your-rovle-ethernet-receiver-or-transceiver/rovl-wiring/rovl-e-pc-board-internal-connections/gnss-compass-main-4-pin-rs-232-connection.md). # GNSS Compass Main (4-pin) RS-232 Connection The GNSS Compass modules drive longer cable lengths than can be done reliably with TTL-level serial signals. The ROVL-ethernet PC board is set up to accommodate this. The GNSS Compass modules expect DC power (Vin) of 4.1V to 5V. {% hint style="info" %} The GNSS Compass main connection is RS-232. Many modern serial ports call themselves "RS-232" but are actually TTL or CMOS level signals of 0V to 3.3V or 0V to 5V. The GNSS Compass modules use actual RS-232 signaling of -12V to +12V with the signal sense inverted from the TTL signals. Connecting a GNSS Compass Module to a TTL serial port will likely damage the TTL port. {% endhint %}