User's Guide

Cellular Modem Option and GSM Antenna
The cellular modem option allows you to control your vehicle when out of wifi coverage range.
The majority of OVMS users choose this option, and you will require it if you want to monitor
your vehicle when away from home or office.
Each OVMS modem module is provided with a Hologram SIM card pre-installed. This low cost
service allows you to get cellular connectivity simply. It also allows you to roam between
countries without worry.
Depending on settings, verbosity towards the OVMS server, rhythm of GPS tracking, etc, OVMS
v3 will use between 1 and 3 Megabytes per month of data (when using the v2 server protocol).
You do not have to use the Hologram service. If you use another cellular provider, the Sim Card
format required is 4FF Nano. Micro Sim cards are hard to recut into the smaller format, so
please be careful to not damage the socket; otherwise, ask your operator for a swap (some do it
for free).
If you are using the cellular option, you should attach a suitable cellular antenna to the module,
using the antenna connector labeled “GSM”.
GPS/GNSS Antenna
Some OVMS vehicles can read the GPS signals from the car communication networks directly,
and do not require any additional hardware. For others, the OVMS v3 modem option also
includes a GNSS/GPS satellite tracking receiver.
If you are using this option, you should connect a suitable active GPS antenna to the connector
labelled “GPS”.
Vehicle Connection
The connection to the vehicle is by the DB9 connector labelled “VEHICLE”. This provides power
to the OVMS module, as well as connection to the vehicle communication networks.
Different vehicles require different cables, so you should refer to the appropriate vehicle section
of this user guide to determine which is correct for yours.
OVMS Server v2
The OVMS Server v2 protocol is a proprietary protocol used to communicate between the
vehicle and an OVMS v2 server, as well as from that server to the cellphone apps. To provide
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