Alcatel‑Lucent MCR1721B Control Module – Power and Relay Unit

The Alcatel‑Lucent MCR1721B is a robust control module designed for power management and relay functions in telecommunications infrastructure. Commonly deployed in central offices, remote shelters, and microwave sites, this module provides reliable switching, voltage monitoring, and alarm generation to ensure uninterrupted operation of critical equipment.

Module Functionality

The MCR1721B serves as an interface between the power distribution system and the network equipment, offering multiple relay outputs for controlling AC/DC loads, as well as digital inputs for monitoring external sensors such as temperature, door contacts, and smoke detectors. Its microcontroller‑based design enables programmable logic control, allowing customised sequences for power‑up, shut‑down, and failover actions.

The unit communicates with the site's supervisory system via a serial (RS‑232/485) or Ethernet connection, reporting status and accepting remote commands. It also features a local display and keypad for manual configuration and troubleshooting.

Technical Specifications

• Product Name: Control Module MCR1721B

• Part Number: MCR1721B

• Relay Outputs: 8 x Form C (SPDT) – 30 VDC / 250 VAC, 5A rating

• Digital Inputs: 8 x isolated (12‑24 VDC or dry contact)

• Analog Inputs: 2 x 4‑20 mA or 0‑10 V (for current/voltage monitoring)

• Communication: RS‑485 (Modbus), 10/100 Ethernet (SNMP, HTTP)

• Power Supply: 48 VDC nominal (36‑72 VDC)

• Power Consumption: 15 W

• Operating Temperature: ‑20°C to +60°C

• Dimensions: 1U x 19 inches rackmount

Key Features

• Programmable logic controller (PLC)‑like functionality with ladder logic support.

• Real‑time clock for scheduled operations (e.g., generator start/stop).

• Event logging with up to 10,000 entries.

• Alarm thresholds configurable per input channel.

• Remote firmware upgrade via Ethernet.

• LED indicators for relay status and communication activity.

Application Scenarios

The MCR1721B is widely used in telecom power systems to control rectifier modules, manage battery banks, and initiate backup generators during mains failure. It can also interface with environmental control units (ECUs) to manage air conditioning and heating based on temperature readings. In microwave sites, it handles antenna de‑icing and radio redundancy switching.

Integration with a network operations centre (NOC) enables centralised monitoring and automated response to alarms, reducing field visits and improving uptime.

Installation and Configuration

Mounting is straightforward using standard 19‑inch racks. The module comes with a terminal block for all field wiring. Configuration is done via a web‑based interface or a simple text‑based terminal. The built‑in test mode allows verification of all relay and input functions without connecting to live loads.

Maintenance and Reliability

Solid‑state design ensures high reliability, with no moving parts. The module includes self‑diagnostics that monitor internal voltage, temperature, and communication errors. In case of failure, the unit can be replaced quickly without disrupting power to the loads, thanks to its redundant power input and fail‑safe relay settings.

Conclusion

The Alcatel‑Lucent MCR1721B Control Module is a versatile, dependable solution for power and facility management in telecom sites. Its rich I/O, programmability, and robust construction make it an essential component for maintaining network resilience and operational efficiency.