Product Description: Johnson Controls Cardkey CG721 (CK721) Network Controller
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Model:Â CG721 (commonly referred to as CK721). The designation “CK721” is the well-known legacy product name from the Cardkey era.
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Part Number:Â 27-5379-714. This is the specific manufacturing part number for this unit.
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Device Type:Â Network Controller / System Controller.
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Condition: USED, This indicates physical damage, likely to the housing or internal components on one side, rendering the unit inoperative. It is suitable for parts, repair, or recycling.
The CG721/CK721 was the central brain of a Cardkey P2000 or System 7000 access control and security management system.
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Core Function: It acted as the main network controller, managing communication between the central computer running the Cardkey software (like P2000) and all the downstream field hardware.
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System Role:
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Communications Hub:Â Connected via RS-485/RS-422 networks (often labeled “Side 1,” “Side 2,” etc.) to door controllers, reader interfaces, and input/output modules.
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Data Processing:Â Stored the system database (cardholders, access levels, timezones, door configurations) and made real-time access decisions.
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Network Interface:Â Typically connected to the host PC via an RS-232 or early Ethernet connection (depending on the specific model/variant).
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Key Details:
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Condition:Â USED, BROKEN FROM SIDE
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Part Number:Â 27-5379-714
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Model:Â CG721 / CK721 Network Access Control Panel
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Legacy System:Â Used with Cardkey P2000, System 7000 software.
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Fault Description:Â Physical/electrical damage associated with communication port Side #3.
Potential Use:
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Source for rare replacement components (boards, chips, connectors).
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Donor for housing, power supply, or undamaged terminal blocks.
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For technicians experienced in repairing legacy Cardkey hardware.
