Also referred to as Dual Nervous Systems, they are the two separate but joined Selyn transport systems found only in channels. RenSimes have only one selyn system and is used exclusively for the intake and personal consumption of selyn from a Gen or channel.
The Dual Selyn System in the channel comprises the Primary Selyn System that is used for the channel's personal Need and personal metabolic functions, and the Secondary Selyn System that is used for storage of selyn that is later transferred to renSimes. The Primary Selyn System is also used to control the channel's Secondary Selyn System
The Secondary Selyn System is what allows channels to perform the various functions that renSimes cannot do with one system.
Also refereed to as Dual Selyn-Storage System
From: House of Zeor, Ch 10. --"The channel is a secondary mutation that differs radically from the basic Sime mutation. One important difference is the dual selyn-storage system. The ordinary Sime can only draw, store, and utilize selyn to sustain his own body functions. The channel too, has this basic selyn transport system. But in addition, the channel has a separate system that is used to gather selyn from Gen donors and to dispense it to Simes.
"This secondary system has a much larger storage capacity. It is a Householding custom that all channels carry about three-quarters capacity. I have about half that right now. It would be sufficient, but it's inaccessible to my personal use. If I die, it all goes to waste."