Secutron MR-2602 Installation Manual page 21

To calculate the wire run distance for any gauge wire and any maximum current value, use the following
formula:
1.25
Remix =
Immix
Amps
Remix × 1,000
Distance =
2(wire resistance in ohms per 1,000
feet)
Secur-bus Capacitance
Maximum wire capacitance for proper operation of the Secur-bus is 90 nF (nanofarad). Typical wire
capacitance for 22 awg quad cable is 20 nF per 1,000 feet. Thus, for 22 awg quad cable, the maximum wire
run distance is ((90/20)× 1,000) = 4,500 feet. Other types of wire have different capacitance values. Consult
the wire manufacturer's data sheets for typical capacitance values.
Shielded wire has a much higher capacitance value and distances are severely reduced.
Note:
The following devices may be connected to the Secur-bus. All devices are supervised. See section for adding
and deleting devices on the Secur-bus.
Devices Description
MR-2605-T
External to control panel.
Up to 4 of each device may be connected.
MR-2605-AT
Mounted inside control panel. See diagram in "3.3
MR-2806
Mounting the MR-2602" on page 9.
1. Do not run the Secur-bus adjacent to sources of high transient noise such as AC wiring, tele-
phone cable bundles or computer wiring.
2. If the Secure-bus must go through a high transient area, use shielded cable.
3. If shielded cable is used, the distances in the chart above are cut in half.
ohms
MR-2602 Installation & Operator's Manual
feet
15