DSC MX920

The DSC MX920 Line Isolator Module is used on IQ PRO panels. It connects to the MX addressable loop circuit of the HSM3105. The MX920 module is used to monitor for short circuits. If it detects a short circuit, it will isolate the affected section while allowing the rest of the addressable circuit to function normally. This module ensures that a single short does not disable the entire MX addressable loop circuit.

In order for an IQ PRO to utilize the addressable loop, it requires that you first add the DSC HSM3105 module. The addition of this module tells the IQ Pro that it will be using MX devices. Without the HSM3105, there is nowhere on the IQ Pro to connect MX addressable devices. The MX920 is a circuit board mounted inside a custom-built fascia plate. It contains a single LED on the face of the fascia plate. The MX920 is designed to be mounted onto a standard dual-gang MK box.

The IQ PRO comes in many variations. It is available in a metal or plastic enclosure. It comes with either a Verizon, AT&T or Telus (Canada) Cellular LTE communicator. Along with a PowerG-wireless-only version, it also comes with optional support for various legacy wireless frequencies. When upgraded to include the MX addressable loop, there are two (2) wiring options to choose from. Either a 4-wire loop configuration or a 2-wire spur configuration. Loop configuration uses the + and (-) terminals from the left loop of the HSM3105, and connects to all MX devices in parallel, including the MX920, and then terminates back at the HSM3105 + and (-) terminals from the right loop. Spur configuration only uses one (1) set of + and (-) terminals from either the left or the right loop and terminates at the end of the single 2-wire run.

The MX920 has six (6) terminals. L+, L-, S+, S-, R+, and R-. The L+ and L- connect to the left-hand side of the addressable loop. The R+ and R- connect to the right-hand side of the addressable loop. So essentially it just sits right in the middle of an addressable loop. The S+ and S- terminals allow you to run a separate 2-wire spur loop off of the MX920.

The MX920 isolator consists of two (2) internal normally closed switches. If a short circuit is detected on the spur circuit (S+ and S-), both switches open. If a short is detected on the left-hand side of the MX loop (L+ and L-), then only the left-hand switch opens. If a short is detected on the right-hand side of the MX loop (R+ and R-), then only the right-hand switch opens. This ensures that wherever a short exists, it gets isolated from the remaining addressable devices on the MX loop.

Current can flow in both directions. When two (2) MX920 Line Isolator Modules are connected in a 4-wire loop configuration, then a short is easily isolated between the two devices. Although it can be used in a two-wire spur configuration, the MX920 works best when connected in a 4-wire loop configuration. Using the loop configuration ensures that the highest number of remaining devices stay active and working in the event of a short circuit on the addressable loop. This is why the loop configuration is preferred when using an MX920.

The terminals on the MX920 are designed for only one (1) wire to be connected per terminal. Recommended wire gauge is 14AWG to 22AWG. The terminals cannot accept wire larger than 2.5mm square, which is slightly larger than 14 AWG wire. Power down your panel, wire the MX920 into your MX circuit and then power the system back up. The MX920 immediately begins protecting your MX addressable loop. If a short is detected, the MX920 isolates it, and the LED on the module lights up providing a visual verification of the location of the short.

Specifications

• Product Type: MX Addressable Loop Isolator
• Dimensions (H xW x D): 3.43" x 5.83" x .55" inches (87mm x 148mm x 14mm)
• Voltage: 11.3VDC - 12.5VDC (from panel) or 40VDC Max with power supply module (HSM2300 or HSM2204)
• Current Draw: 100mA (w/ no devices attached)
• LED: Yes - Red (Indicates a short circuit)
• Mounting Option: Dual-gang MK box
• Operating Relative Humidity: 5% to 93% RH non-condensing
• Operating Temperature: 32°F to 120°F (0°C to 49°C)