ELK-M1DBHR — Data Bus Hub Retrofit Instructions

The ELK-M1DBHR Data Bus Hub Retrofit is designed for retrofit jobs where existing 4-conductor cables are the only wires available. It creates 4 managed RS-485 branches from a single M1 main RS-485 data bus, allowing up to 2 home-run cables per branch (4 branches x 2 each = 8 home runs total).

Important Restrictions

• DO NOT connect more than two (2) M1DBHR hubs to a single M1 Control.
• DO NOT connect an M1DBHR onto a branch of another M1DBHR — it cannot be used as an extender or remote repeater.
• DO NOT mount the M1DBHR remotely away from the M1 — it must be mounted within the main M1 Control enclosure.
• Always terminate the last (end-of-line) device on each home run.

Installation

Mount the M1DBHR inside the main M1 Control enclosure and connect it to the M1's Data Bus terminals (+VKP, DATA A, DATA B, NEG) using a short 4-conductor cable. The M1DBHR provides 5 terminating jumpers:

Branch Wiring Examples

• Branch 1 — 1 home run with 1 keypad: place terminating jumper on the keypad AND on JP2 of the M1DBHR.
• Branch 2 — 2 home runs with 1 keypad on each: place terminating jumpers on BOTH keypads and remove jumper JP3 on the M1DBHR (do not jumper JP3).
• Branch 3 — 2 home runs, each with multiple daisy-chained devices (keypads/expanders): place a terminating jumper on the LAST device on each home run and remove jumper JP4 on the M1DBHR.
• Branch 4 — 1 home run with 2 keypads and 1 expander (daisy-chained): place terminating jumper on the LAST device and on JP5 of the M1DBHR.

The examples above illustrate the flexibility of the 4 data-bus branches; the actual number and type of devices used on each branch is up to the installer.

End-of-Line Data Bus Termination — Critical

• All bus devices (keypads, expanders, etc.) have terminating jumpers. Placing a shorting header on the jumper engages a 120 Ohm resistor across the Data A & B lines. Refer to individual device manuals for shorting header locations.
• Using 1 M1DBHR: place a jumper on JP1 of the M1DBHR and JP3 of the M1 Control.
• Using 2 M1DBHR boards: place jumpers on JP1 of both M1DBHR boards and remove jumper JP3 on the M1 Control.
• DO NOT exceed two (2) terminating jumpers on any of the 4 branches or the main M1 bus.

Specifications

• Maximum wire length of any branch: 4,000 ft (same as the main M1 bus).
• Minimum wire gauge: 24 AWG (18-22 AWG recommended for long distances).

Power Notes

Do NOT connect +VKP to the M1DBHR if it's being powered from an auxiliary power supply. When adding additional data bus devices, calculate the total current draw — if it exceeds the M1 Control's limits, add an auxiliary 12VDC power supply. Connect all Negative (-) wires together to form a common negative reference path.