The name of the organization originates from technology that alows them to quickly coordinate the efforts of their subordinates scattered across the space while maintaining unparalleled level of security -the Synapse Link.  

Technological base: Combining Imperial technologies of psychic hood and life support with Tau knowledge on data transfer and AI systems syndicate's scientists developed a series of implants called Synapse Links or just Links.
When integrated into wearers neural system this modules adjust functions of brain cortex zones responsible for pchycic activities and sensitive experience. The advanced AI is used to process and structure information aggregated by bearers organism in to packages of digital data and send them through the warp utilizing natural ability of all living organisms to emanete and comprehend psychic waves. The build in amplifier empowers this emanations so that even an average person without psychic potential can emit planet-wide. Sophisticated data transfer protocols ensures that information is encripted and the frequency they operate on is secure.  
Together all users equiped with different types of Link modules form a semi-organic network, known as the Nexus, able to exchange data between nodes at unmatched speed allowing knowledge processed by individual user at one end of the galaxy to be received by members of the net on the other end almost simultaneously. Theoretically, this anables an individual person to receive all experience, master every skill and learn entire knowledge gathered at the Nexus in an instant, but limitations of physiology will cause an overload of one's CNS that very moment and then death. Or madness, if lucky.  

The Nexus structure: The net consists of individual users called Nodes ranked into three levels by their power and functions. A unit comprised around single level 3 node is called a Cluster. Each Cluster is fully autonomic and share the same knowledge bank as other Clusters thus even if one or more clusters collapses the whole net remains operational and very little data is lost.   Node's rank is determined by the type of augmentation device used. Evidently there are three categories of such hardware, called Links.  

SLR (Synapse Link Receiver) - the most basic of all Links given to field operatives who has low or none psychic potential. This device is a tiny cybernetic implant connected to bearers neural system and linked to one of the high ranking Nodes allowing him co comprehend data transferred by psychic means. SLR also gather any raw sensitive data aggregated by the user and transmit it to the linked supperior. Above this, implant provides high tech interfaces and protocols for secure low range communication. Inside organization SLR users are known as R-Nodes.  

PAC (Psyche Amplifying Conductor) - this type of Links are given to high ranking operatives possessing a considerable amount of psychic power and may vary in appearance because they are designed to compliment their bearer in a best way possible. They all, however, are external devices cybernaticaly attached to their users neural system. In many ways PACs resemble Imperial psychic hoods - they too allow Psyker to focus and channel their powers but more importantly they allow to use this powers to communicate and transfer information at great distances with a speed of thought. Given special training a psyker with PAC can act like a living wireless router providing access to the Nexus for all SLR users linked to him, transferring their data to cluster's lvl 3 Node and back to his subordinates. PAC has a build in AI to help him process such enormous amounts of information and react to the most relevant stimulus immediately. The reach of a PAC-equipped psyker is limited by the transmitter power. Both his and those he try to contact. For example a SLR transmitter is relatively weak hence a stable connection can be established only on a planetary scale but lvl 3 Nodes are equipped with very powerful transmitters and can sustain a steady link with PAC anywhere inside the sector. As for the direct connection between two PACs - it is only available through standard protocols because Synapse Link between them is prohibited by Nexus design as insecure due to many problems associated with breaking the communication chain, altogether known as the Echo effect. The nature of this effect lies within how Link modules receive, process and transmit data - they do it simultaneously and seamlessly so virtually you can tell that lvl 2 Node knows everything that is known to his linked lvl 1s - this is a lot of data to process even with AI assistance and every PAC psyker is limited in number of linked SLRs by his own power. The moment he attempts to contact another PAC their modules will be overloaded with a double amount of info causing massive brain damage to both and sending two identical data packages further to the net, creating an echo-like signal that disrupts synchronization processes inside the Nexus. Syndicate members refer to PAC users as C-Nodes, Synapses or Amps.  

LMN (Link Magnifying Node) - this Link type is a facility based around a body of a powerful psyker who's life is supported by the same kind of technology used for Space Marine dreadnoughts and outfitted with advanced AI, powerful long range transmitter and a vast data storage. All this equipment occupies a medium size chamber and therefore can only be found on a ground base or a capital ship where it serves as a local overseer managing different aspects of installation functioning and assisting staff in their duties. Each LMN is connected to other LMN units within it's transmitting range and altogether they form the frame of the Nexus. Their powerful transmitters allows them to maintain a stable realtime conduit through several sectors and even at greater distances delay is minor. This undead constructs do all the job of sorting, cataloging and storing immense amounts of knowledge passing through the Nexus. They have full access to information stored at net's databanks and handle all requests for specific info. They are commonly named M-Nodes or Lenses.  

General features: All Synapse Link modules share several traits in common.
The major one - their bearers become immune to all mind confusing effects based on psychic warp-energies since this modules are connected to the brain cortex zones that control psychic activities and tune them to comprehend only specially encrypted frequency used by the Nexus.  
The second noteable feature is their complex fail-safe system that prevents tech from capturing and ensures hundred percent loyalty within it's ranks. Each module is equipped with a small melta charge that explode destroying itself as well as melting a sizable hole in users brain when system registry no vitals or signs of behavior considered disloyal and threatening.  
Links also help psykers conceal their powers in presence of those undesirable, like members of the inquisition.

The first capital letter define the branch and the number indicates the standing within from lower to higher number.

C - command
F - field operation
U - undercover
R - research
M - maintenance

F1 - rookie - blank pad
F2 - crewmen
F3 - operative - two vertical stripes
F4 - chief
F5 - master chief
F6 - commander