Keri Systems SB-293 - Manual (Page 28)

Technical Reference Manual – PXL-250 and SB-293 Keri Systems, Inc.
Page 28 P/N: 01836-004 Revision 5.5
7.7 RS-485 Networking
The PXL-250 uses a half-duplex, RS-485 communication bus. This is a very robust
system and has been tested to exceed standard RS-485 industry specifications. Using
approved cable and good installation practices, the network will operate satisfactorialy
with up to 16,000 feet of cable for systems of up to 128 PXL-250 controllers, each
with an SB-293. The following rules apply when wiring the controller network
communication bus.
1. The total network cable length cannot be greater than 16,000 feet.
2. Controllers can be connected in a single-run multi-drop, a star, mulitple stars, a
continuous daisy chain, etc.
3. The master controller can be located at any point in the network.
4. Care must be take to ensure the Tx- and Tx+ lines are not cross-wired.
5. Shield integrity must be maintained throughout the network installation.
6. If there are more wires than will reliably fit into the PXL-250 terminal block, Keri
recommends using an external terminal strip to combine the cables and then
connect a single wire to the terminal block.
7. The recommended cable is Belden 9501 or its equivalent. This is a single-pair,
twisted, shielded, AWG 24 cable.
Please refer to the PXL-250 Network Wiring Application Note (P/N 01824-002) in the
Appendix for detailed information on extended network configurations.
NOTE: Keri Systems defines a "Star" pattern as multiple sets of daisy chained
controllers all connected to the master controller at the center of the star.
NOTE: Communication buses such as RS-485 often appear to work even if installed
incorrectly, but can have intermittent problems making problem diagnosis difficult.
Failure to properly install an RS-485 network can result in network communication
errors and can cause the access control system to lock up. Although Keri Systems has
lab tested the functionality and data integrity of the extended network configurations,
no guarantees can be given for extended network configurations.
7.8 PXL-250W Jumper Settings
NOTE: Early revisions of the surface mount PXL-250W mislabeled the JP4 jumper as
JP5. All instructions for the JP4 jumper apply to the jumper labeled as JP5 (see
Figure 9-1 on page 39 for the location of the jumper).
On the PXL-250W controller (for use with Wiegand readers), there is only one jumper
that may require setting. JP4 sets the power supply voltage with which the controller
powers the reader (see Figure 7-1 on page 29 and Figure 9-1 on page 39).