PTI Security Systems specifications for Digitech RS-485 systems
The RS-485 network is used by the Syscon to communicate with the various access control devices at the site. An example of such a network is shown below. The blue line is the RS485A type of communications used for electronic devices. Generally, limited to four thousand total feet of wire length. Used for connecting the Falcon XT to AI Devices. data wire.
- Connection is made using an 18 Gauge 2 or 4 conductor cable, that has a foil shield and a bare drain wire. Do not substitute any other wire type.
- The RS-485 network will be a continuous circuit, with no branches. You may be faced with a situation where conduit at a site branches off to multiple buildings. To avoid having a branch in the network, you should run a second 2 conductor wire back in a "loop", or use a 4 conductor wire (2 wires out and 2 back) and then continue on to the next building. See example below.
- Each end of the circuit will be terminated with the appropriate jumper or switch setting (depending on what type of device is at the end). There should only be 2 terminations on a network.
- The Syscon does not have to be at the end of the network. It can be in the middle of the chain if required by the site layout.
- When connecting the devices, that the shield wire is connected at both ends to connector P2. At the Syscon end the shield wire is connected to a valid earth ground. Do not connect the shield wire to earth ground at any location other than the Syscon.
- Maximum total cable distance of the RS-485 network is 4000 feet.
- Splicing of wires should only happen at devices. Do not splice in-between devices, and do not pull a splice into conduit.
- Four conductor cable is only used when it is necessary to "loop back" the RS485A type of communications used for electronic devices. Generally, limited to four thousand total feet of wire length. Used for connecting the Falcon XT to AI Devices. network to avoid having extra branches.
- Because its wire is typically very short (<20 feet) the RS-485 cable to the DigiGraphics (if equipped) does not count as a "branch".
- Termination of the Syscon is done via Jumper J4 on the lower board. RS-485 Keypads and Unimuxes are terminated via a switch located beside the plug for the RS-485 data lines.