quadruped_ros2_control/descriptions/quadruped_gazebo/urdf/common/transmission.xacro

<?xml version="1.0"?>

<robot xmlns:xacro="http://www.ros.org/wiki/xacro">

    <xacro:macro name="leg_transmission" params="name">

        <transmission name="${prefix}_HAA_tran">
            <type>transmission_interface/SimpleTransmission</type>
            <joint name="${prefix}_HAA">
                <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
            </joint>
            <actuator name="${prefix}_HAA_motor">
                <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
                <mechanicalReduction>1</mechanicalReduction>
            </actuator>
        </transmission>

        <transmission name="${prefix}_HFE_tran">
            <type>transmission_interface/SimpleTransmission</type>
            <joint name="${prefix}_HFE">
                <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
            </joint>
            <actuator name="${prefix}_HFE_motor">
                <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
                <mechanicalReduction>1</mechanicalReduction>
            </actuator>
        </transmission>

        <transmission name="${prefix}_KFE_tran">
            <type>transmission_interface/SimpleTransmission</type>
            <joint name="${prefix}_KFE">
                <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
            </joint>
            <actuator name="${prefix}_KFE_motor">
                <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
                <mechanicalReduction>1</mechanicalReduction>
            </actuator>
        </transmission>

    </xacro:macro>

</robot>