# Connecting Readers The AI Security Hub and Security Hub v1 support Accessia Readers and third party OSDP readers The RS-485 connections to the Readers must use a shielded twisted pair with characteristic impedance in the range of 100 to 120 Ohms * For example, Belden 8723 cable is suitable, provided that the two RS-485 connections share a single twisted pair * The RS485 twisted pair must be terminated at both ends with a 120 Ohm +/- 1% resistor * The Hub has this resistor built in and it is optionally connected using the slide switch. If the Hub is at one end of the Reader wiring (this is the usual case, see Figure 1 and Figure 2) slide the switch to turn the line termination on. If the Hub is in the middle of the Reader wiring (this is possible if two readers are connected to the same channel, coming soon, see Figure 3) then slide the switch to turn the line termination off * Connect the shield of the cable to earth using the labelled earth post inside the enclosure ![Figure 1: Channel with single Reader](/files/YwCU6XcaHYhTxiM1EwmF) ![Figure 2: Channel with two Readers, shared cable (coming soon)](/files/Y7tCgOy3eI6QQJGreGAz) ![Figure 3: Channel with two Readers, separate cables (coming soon)](/files/QLCBAHDYGW7AO9vfhR6Y) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.accessia.com/hardware/ai-security-hub-hub-v1/connecting-readers.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.