This documentation refers to a feature which is only available within the simulator.

The sr.robot library contains support for using a simulated radio unit on the robot. Radio transmitters and receivers are attached to various items in the Student Robotics arena. Each transmitter encodes their identity in a machine-readable way, which means that receivers can identify these objects.

Detecting other stations

Each territory in the arena transmits its identity and information about who has claimed it several times per second.

Using the signal strength and bearing of the received radio signals, you are able to determine the distance and direction of a transmitter in 2D space relative to the radio. Therefore, if the robot can detect transmitters that is at a fixed location in the arena, a robot can calculate its exact position in the arena.

The sr.robot library provides this through a radio attached to your Robot, which is can perform a sweep to detect transmitters:

from sr.robot import *
R = Robot()
transmitters =

When called, the sweep function uses the radio reciever to scan for nearby transmitters. It returns a list of Target objects, each of which describes one of the transmitters that were found within range. A detailed description of the attributes of Target objects is provided later in this page.

Here’s an example that will repeatedly print out the bearing and signal stength of each arena transmitter in range:

from sr.robot import *
R = Robot()

while True:
    transmitters =
    print("I found", len(transmitters), "transmitter(s):")

    for tx in transmitters:
        print(" - Transmitter {0} Bearing: {1} with a signal strength of {2}".format(

Claiming Territories

When your radio’s antenna is within a territory, you are within range to claim it. Claiming a territory requires your robot sending two signals to the tower, two seconds apart. You must ensure that your robot is within the range of the territory when both of the signals are sent.

There are two approaches to claiming a territory, depending upon how much control you need over your robots behaviour while it is making a claim.

The simplest approach is to use the claim_territory method, which will take care of sending the signals as well as ensuring that the proper amount of time passes between them:

This function takes a couple of seconds to complete and you must stay within range of the territory for the whole duration it is running for your claim to succeed.

No information is returned from claim_territory.

Alternatively if you would like to be able to control your robot while also making a territory claim, you can instead manage the claim signals directly:

# Do stuff here

Note that when using begin_territory_claim and complete_territory_claim you are also responsible for ensuring that the proper amount of time (two seconds) passes between the begin and the complete signals.

Objects of the Radio System


A Target object contains information about a detected transmitter. It has the following attributes:

A TargetInfo object containing information about the transmitter that was detected.
The measured strength of the signal as a float.
A float giving the angle to the Target in radians.
A bearing of 0 is in front of the robot. Positive bearings are to the robot’s right.


The TargetInfo object contains information about a transmitter. It has the following attributes:

The two character identifier of the transmitter. Valid values are members of the StationCode enum.
from sr.robot import StationCode

for station in StationCode:
The zone id of the robot that currently owns the stations territory. A None value indicates an unclaimed territory.
Remember that you can find out which zone your robot is in using
A boolean value (True or False) for whether or not the territory is locked.
Locked territories are always unowned and cannot be claimed.