With the systemic turn in deliberative democratic theory, there is renewed and broadened emphasis on the inclusion of all affected by a political decision in the making of those decisions. The key enabler of inclusion at a system level is transmission: theoretically, a deliberative system is more democratic if it can foster the transmission of claims and ideas across different sites, especially between informal sites of public deliberation and the more formal institutions of political decision-making. Yet little is known about the mechanisms of transmission in deliberative systems. How, and to what effect, is transmission facilitated in practice? This paper draws on case studies of three promising mechanisms of deliberative transmission: institutional, innovative and discursive. We discuss the key factors that enable or hinder different forms of transmission, and reflect on the ways in which they might be strengthened in deliberative systems. Our analysis suggests that the systemic turn in deliberative democracy should go hand-in-hand with a nuanced understanding of how transmission occurs across different sites. As such, our discussion has important implications for deliberative scholars and practitioners as they go about conceptualizing, studying and steering deliberative democracy at the large scale.