12V AC-AC Power Adapter, 1000mA (1A) Wall Transformer, 2.5mm x 5.5mm Plug, AC12V Linear Power Supply | AC-121B
12V AC-AC Linear Wall Transformer ā 1000mA (1A)
Part AC-121B
The AC-121B is a wall-mount linear AC-to-AC power adapter delivering 12V AC output at 1000mA (1A). It includes a 2.5mm x 5.5mm straight barrel plug, a less-common connector size that should not be confused with the more common 2.1mm plug. Use this transformer only when your device specifically requires 12VAC alternating current (~) and the connector dimensions match.
ā ļø Important: This is a non-regulated AC-AC adapter that outputs 12VAC, not DC. Before ordering, confirm your device label shows 12VAC or the ~ symbol and that it uses a 2.5mm x 5.5mm connector. The output may measure higher than 12V with no load, which is normal for this type of transformer.
Technical Specifications
- Model: AC-121B
- Input: 120V AC, 60Hz
- Output: 12V AC at 1000mA (1A), approximately 12VA
- Connector: 2.5mm (ID) x 5.5mm (OD) straight barrel plug
- Type: Wall-mount linear transformer (non-regulated)
- Older Part Reference: AC-1285B
Common Use Cases & Compatible Devices
- Alarm and Security Panels: Some DSC, Napco, and similar systems that specifically require 12VAC through a 2.5mm barrel connector. Verify the exact model before ordering.
- Intercom Systems: Residential and light-commercial intercom equipment that specifies 12VAC and a compatible 2.5mm x 5.5mm connector.
- Access Control Boards: Low-draw access control panels and keypads requiring 12VAC at no more than 1A with the correct connector.
- Low-Voltage Control Equipment: Commercial or industrial control boards using an OEM 12VAC transformer with a 2.5mm barrel input.
Common Replacement Compatibility
The AC-121B is a replacement for 12V AC transformers using a 2.5mm x 5.5mm straight barrel plug, including older applications associated with part reference AC-1285B. Confirm your original adapter's AC output, connector dimensions, current requirement, and device model before connecting.
Frequently Asked Questions
Q: How do I know if my device needs AC or DC?
A: AC is shown by the ~ symbol or the letters VAC. DC is shown by VDC or the DC symbol. This adapter is not for DC-only devices.
Q: Is a 2.5mm plug the same as a 2.1mm plug?
A: No. The inside diameter is different, so confirm that your device requires a 2.5mm x 5.5mm connector before ordering.
Q: What current rating should my device have?
A: Confirm that the device requires 12VAC and draws no more than 1000mA (1A). The connector dimensions must also match.
Q: Why can a voltmeter show more than 12V?
A: This is a non-regulated linear transformer. Its no-load voltage can measure higher than the rated output until a device is connected.
Q: What should I verify before ordering?
A: Confirm 12VAC output, 120V AC input compatibility, a 2.5mm x 5.5mm straight barrel connection, and enough clearance for a wall-mount transformer.
