Upgrade an old wired burglar alarm without rewiring: Ajax MultiTransmitter explained
If your wired burglar alarm still detects reliably but the control panel is dated, you do not have to pull out the cables. Ajax MultiTransmitter Jeweller connects up to 18 existing wired detectors to an Ajax hub by radio, so they work in the Ajax app next to new wireless devices. For a single detector, Transmitter Jeweller does the same job from inside the detector's own case. The old panel goes; the sensors and cable runs stay.
Below: when it works, what to check and prices for the Ajax products we supply.
When is it worth keeping the wired detectors?
Often the panel, keypad and signalling have aged while the cable and detectors are sound. Keeping the wiring avoids lifting floors and chasing walls, and makes sense when:
- every detector passes a walk test and its tamper circuit is intact;
- you know how each zone is wired (NC, NO or end-of-line resistors) and the resistor values;
- the cables show no damage, rodent bites or corroded joints;
- the detectors suit the risk (see grading below).
If the old panel dials out over a phone line, Ofcom says BT plans to retire its old landline network by 31 January 2027 and asks anyone with a security alarm on the phone line to tell their provider first.
What does MultiTransmitter Jeweller actually do?
It is an integration module, not a control panel. It passes the alarm, tamper and fault states of wired detectors to an Ajax hub over Jeweller radio, so you arm, disarm and get alerts in the Ajax app. Ajax's figures:
| Feature | MultiTransmitter Jeweller |
|---|---|
| Wired zones | 18, each set to NC, NO, EOL, 2EOL or 3EOL (2EOL and 3EOL on the current version, boxed with a 3EOL label) |
| Cable to detectors | up to 400 m |
| Radio range to the hub | up to 2,000 m in open space |
| Power | 100 to 240 V mains, plus a 12 V backup battery (4 Ah or 7 Ah recommended, not included) |
| Power for detectors | three 10.5 to 15 V outputs, one reserved for fire detectors, 1 A in total |
| Grade | Grade 2 (EN 50131); Ajax also lists PD 6662:2017 |
With EOL, 2EOL or 3EOL wiring it reports a cut or shorted cable straight away. It is for indoor use, at least 1 m from the hub. It will not work with another maker's panel; the Ajax hub replaces it.
MultiTransmitter or Transmitter Jeweller?
Transmitter Jeweller is the single-device version. It fits inside the wired detector's housing (it needs 110 x 41 x 24 mm of space) and runs on batteries, which suits a contact in an outbuilding, a gas or leak detector, or one sensor far from the rest.
| MultiTransmitter Jeweller | Transmitter Jeweller | |
|---|---|---|
| Devices | 18 wired zones | 1 device plus its tamper |
| Power | Mains with 12 V backup battery | Three CR123A batteries (included) |
| Power out to detectors | 10.5 to 15 V, up to 1 A in total | 3.3 V, up to 125 mA |
| Cable length | up to 400 m | up to 130 m |
| Grade | 2 | 2 |
| Our price inc VAT | £130.38 | £53.07 |
A 12 V detector cannot run from the Transmitter's 3.3 V output and needs a separate supply (Ajax warns against wiring another supply into the Transmitter's terminals). Prices include VAT, delivery is extra and prices can change. Both modules sit with our other zone expanders.
Which hub, and how long will the battery last?
Ajax's manual lists Hub 2 (2G), Hub 2 (4G), Hub 2 Plus and the Superior Hub Hybrid (2G) and (4G) as compatible, on OS Malevich 2.13 or later. Each wired device on the module takes one of the hub's device slots.
- Hub 2 (2G) Jeweller: up to 100 devices, £161.53
- Hub 2 (4G) Jeweller: up to 100 devices, two SIM slots, up to 4G, £228.45
- Hub 2 Plus Jeweller: up to 200 devices, adds Wi-Fi, £268.10
Worked example. Say 12 wired detectors draw 180 mA in total on standby (add up each datasheet figure). Ajax lists the module's own quiescent current as 14.6 mA, so the load is about 0.195 A. A 7 Ah battery divided by 0.195 A gives roughly 36 hours; a 4 Ah battery gives about 20. Treat these as upper estimates (older batteries hold less charge) and keep the load under 1 A. We stock 12 V sealed lead-acid alarm batteries.
Can wired smoke detectors stay on the system?
Yes, on the dedicated fire line (marked +EXT). Ajax's manual explains that wired fire detectors need a power reset to recover after an alarm, so they need their own output, shared with nothing else. You can also add Ajax wireless fire alarms to the same hub.
In rented homes in England, the Smoke and Carbon Monoxide Alarm (England) Regulations require at least one smoke alarm on each storey with living accommodation, and GOV.UK's guidance for landlords recommends alarms that comply with BS 5839-6. Check the kept detectors against that.
What happens to grading, police response and insurance?
NSI Technical Bulletin 0001 (2005) says that, tamper arrangements aside, a system takes the grade of its lowest-graded component. Ajax lists MultiTransmitter Jeweller, Transmitter Jeweller and the Hub 2 family as Grade 2, and your old detectors keep whatever grade they had. For Grade 3, Ajax makes Superior MultiTransmitter G3 Jeweller (£146.23) and the wired Superior MultiTransmitter Fibra (£129.95), used with a Grade 3 hub such as Superior Hub Hybrid 2 (£410.12); on a Hub 2 the system stays Grade 2. Ajax says Superior devices are installed and administered by accredited Ajax partners.
NSI explains that under National Police Chiefs' Council (NPCC) policy in England, Wales and Northern Ireland, a system needs a police-recognised installer, an approved alarm receiving centre and a unique reference number (URN), and that monitored systems installed since June 2019 must conform to PD 6662:2017 and BS 8243. Scotland follows Police Scotland's own policy. If your insurer requires an alarm, check the policy wording first.
Zenith is a supplier: we do not fit or maintain alarms. Ajax's manual says the system should be designed and installed by professionals. We can recommend a qualified installer depending on the job and area.
Keep wired, go wireless or move to Fibra?
| Your system | Sensible route | Main Ajax parts |
|---|---|---|
| Sound cable and detectors, panel past it | New hub, keep the detectors through a module | Hub 2 family plus MultiTransmitter |
| Detectors failing or wrong for the risk | Replace them | Wireless detectors such as MotionProtect U |
| Grade 3 wanted and new cable runs possible | Hybrid hub with Ajax Fibra wired devices on 4-core cable | Superior Hub Hybrid 2 |
If you would rather have wired zones on the panel itself, the Hikvision AX PRO Ultra hybrid panel has 16 built in; see our AX PRO buying guide.
Our take
If the wiring is sound, MultiTransmitter is a tidy way to modernise: the old panel goes and detectors you already paid for return with app control and Ethernet plus mobile signalling. Test every detector, note the resistor values and size the battery to the load. For one or two wired devices, Transmitter Jeweller costs less. For Grade 3 or police response, plan the job with an accredited installer from the start.
Want us to check your parts list? Call us on 01902 902251 or send us your zone list, and browse the full Ajax wireless alarm range. We ship nationally to England, Scotland and Wales.
Upgrading a wired alarm: quick questions
Can I convert my wired alarm to wireless?
Keep the wired detectors and replace the panel with an Ajax hub; a MultiTransmitter links up to 18 of them by radio.
Will MultiTransmitter work with my existing control panel?
No. It works with Ajax hubs only, so the old panel is removed.
Do I need new cables?
Not if the existing runs are sound. Each zone can run up to 400 m of cable.
Do wired detectors count towards the hub's device limit?
Yes. Each one takes a device slot, shared with wireless devices: up to 100 on Hub 2 (2G) and Hub 2 (4G), and 200 on Hub 2 Plus.
Source: Ajax Systems blog, August 2020. Product figures from Ajax's MultiTransmitter Jeweller specifications, MultiTransmitter manual and Transmitter manual. UK sources: Ofcom, landlines going digital; NSI, Intruder alarm systems; NSI Technical Bulletin 0001; GOV.UK, smoke and CO alarm regulations Q&A.
