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The Sierra Radio Systems SIR-321 is a general purpose GPIO module for the Sierra Station Controller range.
It provides a flexible mix of relay outputs, open-collector outputs, voltage monitoring inputs, digital inputs, and temperature probe connections, making it one of the most useful expansion modules in the Sierra Station Controller system.
The SIR-321 can be used for station automation, remote site monitoring, repeater control, shack control panels, relay switching, voltage monitoring, alarm inputs, and temperature monitoring. It connects to the Sierra DCN, or Device Control Network, allowing it to be monitored and controlled from a compatible Station Controller host such as the SIR-310 Raspberry Pi Host Adapter.
Key Features
- General purpose GPIO module for Sierra Station Controller systems
- 4 small-signal 2A SPST dry contact relays
- 4 open-collector outputs for controlling external 12V relay coils
- 4 x 0-50V DC voltmeter inputs
- 4 opto-isolated digital inputs
- 2 digital temperature probe inputs
- Control over Sierra DCN
- Useful for station automation, monitoring, and remote control
- Suitable for repeater sites, remote HF stations, and local shack automation
- Can be used with optional external relay accessories
- Compatible with the wider Sierra Station Controller module range
Typical Uses
- Switching station accessories on and off
- Controlling larger external relays
- Monitoring DC supply voltages
- Monitoring battery, solar, or power system status
- Reading door, alarm, fault, or switch closure inputs
- Temperature monitoring with compatible digital temperature sensors
- Remote HF station control
- Repeater site monitoring
- Shack automation and control panel projects
- Triggering other DCN actions from digital inputs
Station Controller System Role
The SIR-321 provides general purpose input and output capability for the Sierra Station Controller system.
It can be used to monitor real-world station conditions and control external equipment through relays or open-collector outputs. This makes it suitable for a wide variety of jobs, from simple equipment switching to more advanced remote-site monitoring.
The module communicates over the Sierra DCN, using RJ45 style connections and network-style patch cables. These DCN connections carry Sierra’s RS-485 based control data and system power between compatible modules.
Although the connectors are RJ45 style, the DCN ports are not standard Ethernet ports and should only be connected to compatible Sierra Station Controller modules and accessories.
I/O Connections
| Function | Details |
|---|---|
| Internal relays | 4 x small-signal 2A SPST dry contact relays |
| Open-collector outputs | 4 x outputs for controlling external 12V relay coils |
| Analogue voltage inputs | 4 x 0-50V DC voltmeter inputs |
| Digital inputs | 4 x opto-isolated digital inputs |
| Temperature inputs | 2 x digital temperature probe inputs |
| Control interface | Sierra DCN |
| DCN connection | RJ45 style DCN connection |
Specifications
| Specification | Details |
| Brand | Sierra Radio Systems |
| Model | SIR-321 |
| Product type | General Purpose GPIO Module |
| Module type | Station Controller I/O module |
| Internal relays | 4 x SPST dry contact relays |
| Relay rating | 2A small-signal |
| Open-collector outputs | 4 |
| Voltage monitoring inputs | 4 |
| Voltage monitoring range | 0-50V DC |
| Digital inputs | 4 opto-isolated inputs |
| Temperature probe inputs | 2 |
| Control method | Sierra DCN |
| System type | Sierra Station Controller |
Compatible Sierra Station Controller Products
The SIR-321 is designed for use within a Sierra Station Controller system. It is typically used alongside a compatible host, such as the SIR-310 Raspberry Pi Host Adapter, and can be expanded with suitable DCN hubs, relay accessories, temperature sensors, and control wiring.
Important Note
This listing is for the SIR-321 General Purpose GPIO Module only.
SIR-310 host adapter, installation kit, DCN hub, temperature probes, external relays, RCA cables, power supply, station equipment, and other accessories are not included unless stated otherwise.
The Sierra DCN uses RJ45 connectors and network-style cables, but DCN connections are not standard Ethernet connections. Do not connect DCN ports directly to normal Ethernet network equipment.
A suitable 12V DC supply is required when the module is not being powered through a Sierra DCN connection from the SIR-310 host adaptor.
Shipping & Delivery
We offer UK and international delivery services, including next working day and selected weekend options for eligible orders. Available services, prices and estimated delivery times are displayed at checkout.
Delivery Information
Delivery options depend on the parcel's size, weight, contents and destination. Express and weekend services are subject to availability and cut-off times. Oversized or exceptionally heavy items may require a specialist delivery quotation.
Returns & Cancellations
To arrange a return, please contact ML&S or complete our returns form. You may also exercise your statutory right to cancel by email or another clear statement, without completing the form.
Changed Your Mind?
Under the Consumer Contracts Regulations 2013, most purchases made online or by telephone can be cancelled within 14 days of receipt.
You must notify us of your cancellation within this period and return the goods within a further 14 days.
Please handle all goods with care. Returned items must be in a resaleable condition, complete with their original packaging, and all supplied accessories.
You may inspect goods as you would in a shop. Handling beyond what is necessary to inspect them may result in a lawful deduction for diminished value.
Exceptions
Modified Equipment & Reversal Charges
Additional return conditions may apply to equipment modified at the customer's request, including wideband transmit or receive modifications.
ML&S may charge a reasonable fee to reverse physical modifications and restore the equipment to its original factory specification. Any such charge will be agreed in advance and deducted from your refund.
Custom-Made Cable Assemblies
Coaxial cable assemblies manufactured to a customer's specifications are excluded from the 14-day return policy and are non-refundable unless faulty.
Software & Labour Charges
Labour and modification charges requested by the customer are non-refundable once the work has been completed.
Computer software may only be returned under the 14-day return policy if it remains sealed and unopened.
Return Postage Charges
Customers are responsible for the direct cost of returning unwanted or incorrectly ordered goods, where permitted by law. You may arrange your own suitable return postage or use one of our optional prepaid services.
Standard Parcels
Royal Mail Return Label
£5.95
Per parcel
For eligible standard-sized parcels, subject to Royal Mail restrictions. Free collection included.
Larger Parcels
DPD Return Label
£7.95
Per parcel
For larger or heavier parcels and any shipments with batteries.
Collection Service
DPD Collection
£25.00
Per parcel
Available upon request for eligible addresses, subject to availability.
Prepaid return charges will be confirmed before booking and deducted from your refund.
These prices apply to eligible UK mainland returns. Oversized items, specialist products and returns from other destinations may require a separate quotation. Estimated return costs will be disclosed before purchase.
Faulty or Incorrectly Supplied Goods
Return postage charges do not apply to faulty, damaged or incorrectly supplied goods returned under statutory rights. ML&S will arrange a free return in these circumstances.
Refunds
Refunds are processed without undue delay following receipt and inspection of returned goods, and no later than 14 days after we receive goods returned under statutory cancellation rights.
Refunds will be issued to the original payment method. Any prepaid return postage charges or lawful deductions for diminished value will be itemised.
Warranty Terms & Conditions
New Equipment Warranty
Minimum 2-Year Warranty
All new products supplied by ML&S carry a minimum two-year warranty against manufacturing defects, excluding batteries, which are covered by separate warranty terms.
Some manufacturers provide extended warranties, such as the three-year warranty available on eligible Yaesu equipment. Any additional coverage is subject to the manufacturer's terms and conditions.
Our workshop may assess and repair faulty equipment on site or refer it to the manufacturer or an authorised service centre where necessary.
Warranty exclusions may include batteries, normal wear and tear, accidental damage, misuse and unauthorised modifications, as specified in the applicable warranty terms.
All warranties are provided in addition to your statutory consumer rights against ML&S, which are not limited by the warranty period.
International Returns & Warranty
Unless otherwise stated, ML&S warranty servicing is carried out in the UK. International customers must contact us before returning goods to confirm shipping and customs requirements.
International customers are responsible for return postage unless the goods are faulty and ML&S has been notified within a reasonable time.
ML&S accepts no responsibility for additional charges resulting from incorrectly completed customs documentation. Any additional duties charged to ML&S as a result will be billed to the customer before return of the goods.
Need Help With a Return?
Our team can assist with returns, postage arrangements, modifications and warranty claims.
Nothing in these terms excludes or limits your statutory consumer rights.