# Door contact sensor BLOW 4921# model HO-03C white, magnetic reed switch

**URL:** https://aio.lv/en/product--blow-4921--11863480
**Data updated:** 2026-03-09 17:40 (EET)
**Category:** Smart Sensors
**Manufacturer:** BLOW
**Manufacturer code:** 4921#
**EAN:** 5900804098928
**Warranty:** 2 Years
**Availability:** Available for order
**Price:** 5.49 €
**Prices and availability valid until:** 2026-07-15 23:59
**Price without VAT (21%):** 4.54 EUR
**Can be purchased by legal entities:** Yes (invoice)
**Buy:** https://aio.lv/en/product--blow-4921--11863480

## Delivery options

| Delivery method | Delivery time | Cost |
|---|---|---|
| Office pickup (2b. Kengaraga str., Riga, Latvia, LV-1063) | 08.07.2026 | free |
| Pickup points | 13.07.2026 | 1.99 EUR |
| Courier delivery to door | 13.07.2026 | 4.99 EUR |

## Summary description

Wired door contact sensor BLOW 4921# (HO-03C) in white. Magnetic reed-switch sensor designed to detect opening and closing of doors or windows and integrate with alarm or security systems. Compact housing and two-part design allow easy surface mounting on frames; suitable for residential and commercial intrusion detection and access monitoring.

## Long description

Wired door contact sensor BLOW HO-03C in white is a magnetic reed-switch device designed to detect the opening and closing of doors and windows and to integrate with wired alarm and security systems. The sensor consists of a compact two-part housing — a main sensor body and a magnet — that are mounted on a door/window and frame. Its low-profile design and wired connection make it suitable for reliable intrusion detection and access monitoring in residential and commercial installations.
Advantages
The BLOW HO-03C provides a simple and reliable switching mechanism based on a magnetic reed contact, ensuring consistent detection of open/closed states. Its compact two-piece design supports unobtrusive surface mounting and straightforward alignment. The wired interface avoids battery dependence and reduces maintenance needs, while the white finish blends with many door and window frames. The mechanical construction offers stable performance in standard indoor environments.
Suitable for
 Wired alarm and security systems for homes
 Office or commercial access monitoring
 Monitoring of windows, doors, shutters and sliding panels
 Integration into alarm control panels, input zones or relay modules
Key specifications
 Type: Wired magnetic reed switch door/window contact
 Design: Two-part sensor and magnet for surface mounting
 Color: White housing
 Contact operation: Normally closed/normally open wiring options depending on system connection
 Mounting: Surface mount on door/window and frame; compact low-profile housing
 Environment: Intended for indoor use in residential and commercial settings
 Connection: Wired electrical connection for integration with alarm panels
How to use
Mount the sensor body on the stationary frame and the magnet on the moving door or window so that the two parts align within the specified gap when closed. Connect the sensor leads to the corresponding input zone of the alarm or security control panel following the panel wiring diagram and the chosen normally closed or normally open configuration. Verify correct operation by closing and opening the door or window and confirming the control panel registers the state changes. Securely fasten the components with screws or adhesive as appropriate for the installation surface.
Usage recommendations
Install the sensor in a dry, protected indoor location away from direct exposure to weather. Keep the alignment gap minimal and consistent to ensure reliable switching. Use the wired connection to route to the control panel with proper cable management and strain relief. For optimal long-term performance, periodically inspect mounting and wiring connections and ensure the magnet and sensor faces are free from debris or paint that could interfere with operation.

## FAQ

### How much does the Door contact sensor BLOW 4921# HO-03C cost, and is it available for purchase?

The price is 5.49 € (valid at the time of publication and already includes all taxes). The item is available for order — 23 pcs. are in stock, and you can place your purchase right now with delivery across Latvia and Europe or choose pickup at the Riga collection point. We offer favorable purchase terms, including the option to split the payment into convenient monthly installments. Availability and price are updated in real time, so we recommend placing your order in advance.

### If I order this product today, when will I receive my order?

If you place your order today, delivery will be as fast and convenient as possible. You will be able to pick up your order on 08.07.2026 at the Riga pickup point or choose delivery across Latvia and Europe. We carefully inspect every purchase and pack it securely for safe transportation.

### What payment options are available?

AiO.lv offers several payment methods: Bank transfer, Bank cards on-line, Apple Pay, Google Pay. All transactions are 100% secure and encrypted.

### Can this product be purchased for a company (with VAT)?

Yes. AiO.lv works with legal entities in Latvia and across Europe. The product price already includes VAT. For certain product categories, as well as for companies from other EU countries with a valid VAT number, a 0% VAT rate may apply. We issue the invoice immediately after the order is placed, support electronic BIS invoices, and automatically generate all necessary accounting documents. You can complete the purchase for a company online — simply select the company profile and choose bank transfer as the payment method during checkout.

### What is the warranty period?

All BLOW products come with an official 2 Years warranty. It covers all manufacturing defects and malfunctions that may occur during use. The warranty is valid at all authorized BLOW service centers and through AiO.lv

### Can the product be returned after purchase?

Yes, you can return the product within 14 days of purchase if you bought it as a consumer (not a legal entity). Returns are possible without giving any reason — the main condition is that the product retains its original appearance and full set of accessories. We will make the process as simple and convenient as possible: just contact our customer support team, and we will help you arrange the return.

### Where should I contact for warranty service?

For warranty-related questions you can contact the AiO.lv (SIA VSPRO) customer support team. More information about warranty service: https://aio.lv/en/warranty

## Image

https://aio.lv/img/cache/product/11863480/67262045_large.webp