There's not much to the little RockBLOCK 9603 itself. There's only one connector for both power and data. There are a couple of status LEDs. Besides some mounting holes, that's pretty much it. A nice tidy little package.


  1. RXD Serial output from RockBLOCK, so it's really TX
  2. CTS Clear to Send (output from RockBLOCK)
  3. RTS Ready To Send (input to RockBLOCK)
  4. NET Network Available
  5. RI Ring Indicator (active low)
  6. TXD Serial input to RockBLOCK, so it's really RX
  7. SLP Sleep control (pull to ground to switch off)
  8. 5V 5V in power supply (450mA limit)
  9. BAT 3.7V power supply (450mA limit)
  10. GND Ground
The RockBLOCK 9603 operates at 3.3V logic level.
Serial Baud Rate is 19200.


The connector on the RockBLOCK modem is a Molex PicoBlade. The mating connector housing is Molex part number 51021-1000. Bare connectors are available in Molex product series 50079 or 50058, but need a special (very expensive) crimping tool. There are also pre-crimped cables available in Molex product series 79758.

You can get these on DigiKey:

With these parts you can make custom cable assemblies.

You do not need these items if your are using the supplied USB cable or the available accessory cable.

LED Indicators

There are two small LED indicators on the side with the big capacitors.

  • Red = DC power present.
  • Green = Capacitors are charged. This is needed for satellite communication.


This is the antenna which talks to the satellites. Make sure it has a good clear view of the sky. Butter side up!

An external antenna can be attached via the coaxial connector on the side. But in this guide we show basic usage with the built in antenna.

Mixed Power/Logic Warning on SLP Pin

Due to a design change in the on/off control circuit, there is a potential issue when interfacing with 3.3V logic level devices. Starting with the v3.F version of the hardware, the SLP pin requires special attention. More info here:

If the RB was supplied by 5V, the connecting device should also be 5V tolerant. If not, it is recommended to use an interfacing circuit, eg MOSFET, transistor, relay, etc. to connect to a microcontroller.

The hardware version number is printed on the antenna side of the RockBLOCK modem.

This guide was first published on Apr 08, 2020. It was last updated on Jun 16, 2024.

This page (Hardware) was last updated on Jun 03, 2024.

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