Migration alternative · NEC

An alternative to NEC phone systems — what to assess and how to migrate

Q: What is the smallest sensible system for a small office?

It depends on the trunk and analog counts. The OM20G is the one-box option: 24 SIP trunks, up to 4 analog ports ordered as 4 FXS, 4 FXO or a 2+2 mix, 16 GB of internal storage, extension numbering from 200, and the only model in the range that can dial out over a 3G/4G USB modem. Tell us the extension and line counts and we will confirm the model rather than guess upward.

Small and mid-size offices usually change phone systems for practical reasons: a lease ends, an office moves, or the maintenance route changes. This page is the assessment for planning a change from an NEC phone system onto an equivalently capable SIP-based alternative: what to inventory, how the numbers and the analog lines are handled, how analog handsets and existing cable can stay in service, how the cutover is phased and what the supporting services need. NEXVIA supplies and integrates the equipment. No competitor models, specifications or prices are published on this site, and nothing here is a claim about the vendor.

Aimed at the small and mid-size office: a one-box IP PBX from 24 SIP trunks with up to 4 analog ports, through models to 1000 trunks
An equivalently capable alternative approach on standard SIP — the same services planned around the site, not around a vendor catalogue
Numbers are preserved by design: extension numbering starts at 200 and can follow your scheme, with a 500-entry route table for translation and directed routing
Analog lines can stay on FXO ports as the fallback path; on the OM20G a 3G/4G USB modem can dial out when the wired line fails
Cabling is reused where possible: the PN1 carries network and power over a two-core pair up to 1600 m for the network function without power; X303-2 Wire and H1-2 Wire are the endpoints
No NEC model numbers, specifications or prices are published on this site, and no disparaging statement about the vendor appears here

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OM20G all-in-one IP PBX with four voice ports, WAN and PC ports and USB modem support

The short answer

For a small or mid-size office, the practical question is what the smallest sensible system looks like and what has to be kept. The equivalently capable alternative approach here is a standards-based SIP platform sized from the site: the OM20G starts at 24 SIP trunks with up to 4 analog ports in one box and a 3G/4G USB modem option for outbound calls when the wired line fails; the range runs up to the OM1000-UC at 1000 SIP trunks. Extension numbering starts at 200 and can follow the scheme staff already know, and a 500-entry route table handles number translation and directed routing.

Keeping what works is the point of the plan. Analog lines stay on FXO ports as the fallback path — an outbound SIP trunk call that times out or returns a 4xx/5xx/6xx response is routed out over the analog line instead — and analog handsets stay in service through the GA10 (2 SIP lines, 1 FXS port) or through the analog ports on the PBX, up to 4 / 12 / 48 / 96 by model. Fax machines keep working as T.38 or G.711 pass-through.

Where the cabling is old, it can often stay: the PN1 carries network and power over a two-core pair, up to 1600 m for the network function without power, and the PN8 and PN24 switches carry 8 and 24 two-wire devices at up to 300 m for network plus power, with X303-2 Wire and H1-2 Wire at the endpoints. Desk phones publish 2 SIP lines (X301 group) to 20 (X7, X7C, X210) with integrated PoE on the P, G and W variants — one cable per desk. No NEC models, specifications or prices appear on this site; the configuration is confirmed on the quotation.

Migration decision sheet

Decision area	What to inventory	How we handle it
Size the system from the site	Extension count, outside-line count, sites to link, whether the office keeps analog lines; one box or a rack	The OM20G is the one-box office system: 24 SIP trunks, up to 4 analog ports, 16 GB storage, a built-in OpenVPN client and the only model with a 3G/4G USB modem; the range steps to 62, 216, 496 and 1000 SIP trunks as the site grows.
Keep the numbers and the dial plan	Existing extension ranges and lengths, the main number and any published DID numbers, night-service behaviour, speed-dial habits	Numbering starts at 200 and can mirror the existing scheme; a 500-entry route table handles number translation and directed routing; ring groups take up to 40 members and queues up to 20 waiting calls; auto attendant with time-of-day routing covers out-of-hours calls.
Decide the outside-line strategy	Analog lines that remain, SIP trunks from a carrier, a cellular fallback route, the number of simultaneous calls needed	SIP trunks as direct, registration or registered-by types with TLS available; analog lines on FXO ports as the escape path when a SIP trunk call times out or fails with 4xx/5xx/6xx; on the OM20G, outbound calls can also run over a 3G/4G USB modem.
Decide what happens to handsets	Analog handsets that can stay; desk positions that move to SIP phones; headsets and answering positions	GA10 for one analog telephone, or FXS ports on the PBX for several; replacement desk phones publish 2, 4, 6, 12, 16 or 20 SIP lines with a 6-way conference and EHS headset support, and integrated PoE on the P, G and W variants.
Decide what happens to the cabling	Desks with a data outlet; rooms or wall positions on a two-core pair; whether cabling can be replaced during the change	One PoE cable per desk where a data outlet exists; PN1 on a two-core pair (up to 1600 m for network without power); PN8 and PN24 for 8 and 24 two-wire devices at up to 300 m for network plus power; X303-2 Wire and H1-2 Wire as the endpoints on that pair.
Plan the cutover window	Whether the office can close for an evening or has to change over live; who answers calls during the switch; how the two systems share the lines	A phone that publishes several SIP accounts can hold registrations on both systems while its block moves, and the old system keeps answering until its last extension has changed — so the change can be a single window or a phased sequence, agreed per site.
Keep the supporting services	Fax, door entry, alarm lines, overhead paging, voicemail, recording, conference positions	Fax as T.38 or G.711 pass-through; door stations as SIP endpoints with release relays; speaker lines from the PA2S or PA3 gateways at 10–30 W mono; recording in G.711 and G.729 with voicemail and auto attendant as published platform features.

The rows below are decisions and options, not claims about another vendor: this site publishes no competitor model numbers, specifications or prices.

Other migration pages

Avaya alternative

Planning a change from an Avaya phone system: what to inventory, how analog handsets and cabling can be kept, and how a SIP system is phased in alongside the existing one.

Cisco alternative

Assessing an alternative to a Cisco phone system: dial plan, ring groups, pickup and paging rebuilt on a SIP platform, with the existing cabling and analog lines kept where they work.

Mitel alternative

Planning a change from a Mitel phone system: room and corridor handsets, analog ports and two-core cable handled as one assessment, with the cutover phased.

What an alternative to NEC means on this page

It means an equivalently capable alternative approach sized to the site: a standards-based SIP system built from an IP PBX, desk phones, wireless handsets where needed, door stations and paging, with analog lines and handsets kept where they still work. For a small office that is usually one box with up to four analog ports; for a larger site it is a rack model with cards and up to 96 analog ports.

No NEC models, specifications or prices are published on this site, and no judgement about the vendor appears. The assessment is made against your inventory: extensions, lines, positions and cable, with each published figure attached to a real requirement.

Sizing from the published range: 24, 62, 216, 496 and 1000 SIP trunks, with analog ports from none to 96
Standard SIP as the base: registration over SIP with TLS and SRTP options, DTMF as RFC2833, in-band or SIP INFO, codecs covering G.711, G.729A, G.722 and G.722.2
A fallback path that survives a broadband fault: analog lines on FXO ports, and the 3G/4G USB modem option on the OM20G
No disparaging statement about the existing vendor is made anywhere in this assessment

If a requirement depends on a fact we do not hold about the existing installation, we confirm it with you in writing instead of assuming it.

The migration path, step by step

For a single office the change is short; for a group of sites it is a sequence. Either way the order below keeps the numbers, the lines and the fallback path intact.

1. Inventory. Extensions, outside lines, positions and cable, plus everything that is not a desk phone: fax, door, alarm, paging and any line whose purpose is not obvious.
2. Size the platform. Count SIP trunks and analog ports, then pick the model: OM20G (24 trunks, up to 4 analog ports, 3G/4G USB modem) through OM1000-UC (1000 trunks, no analog ports, dual hot standby).
3. Keep the numbers. Extension numbering starts at 200 and can follow the existing scheme; a 500-entry route table handles translation and directed routing; the main number is served by auto attendant with time-of-day routing.
4. Settle the lines. Configure SIP trunks as direct, registration or registered-by with TLS; keep the analog lines on FXO ports as the escape route for calls that time out or fail with 4xx/5xx/6xx; add the cellular fallback where the model supports it.
5. Keep the analog estate working. GA10 for one analog telephone (2 SIP lines, 1 FXS port) or FXS ports on the PBX for several; fax as T.38 or G.711 pass-through.
6. Reuse the cabling. One PoE cable per desk where a data outlet exists; PN1 over an existing two-core pair (up to 1600 m for network without power); PN8 and PN24 for 8 and 24 two-wire devices; X303-2 Wire and H1-2 Wire at the endpoints.
7. Cut over in a planned step. Either a single window or a phased sequence: a multi-account phone can hold registrations on both systems while its block moves, and the old system answers until its last extension has changed.
8. Confirm the details in writing. Model, port cards, line types and the current facts are confirmed on the quotation against the inventory.

What usually stays, and what it needs

A small office change usually reuses more than it replaces. Each row below pairs an existing element with the published figure that decides whether it stays.

Reuse assessment for a changeover to a SIP system, with the published figures

Existing element	Can it stay?	What it needs
Analog outside lines	Yes — worth keeping as the fallback	FXO ports on the IP PBX (up to 4 / 12 / 48 / 96 by model); a SIP trunk call that times out or returns 4xx/5xx/6xx escapes to the analog line. The OM20G also supports a 3G/4G USB modem
Analog telephones	Yes	GA10 adapter (2 SIP lines, 1 FXS port) or an FXS port on the PBX card
Fax machines	Yes	FXS port or GA10; fax as T.38 or G.711 pass-through, with T.38 recommended where both ends support it
Two-core cable to a desk, room or wall position	Often yes	PN1 converter (up to 1600 m for network without power); PN8 or PN24 switches for 8 / 24 devices at up to 300 m for network plus power; X303-2 Wire and H1-2 Wire endpoints
Data cabling and PoE switch ports	Yes	PoE desk phones: integrated PoE is published on the X303P/G/W and X301P/G, so one cable serves the desk
Overhead paging and speaker lines	Yes	PA2S or PA3 paging gateway at 10–30 W mono output, with a line output for an external active speaker
Door and gate positions	Replaced or integrated	SIP door and indoor stations with release relays, registered on the same extension plan

Wi-Fi is not published for every desk model, and Bluetooth is not stated for the X300 Series — where a value is not stated in the manufacturer material, this site says so and confirms the requirement per model.

What this site does not publish

This site publishes no competitor model numbers, specifications or prices, and makes no comparative or disparaging claim about another vendor. A migration decision deserves data that can be checked, so the table above is deliberately built from what has to be assessed and from the published figures of the equipment we supply.

Everything factual on this page is carried from the product documentation — capacities, port counts, escape-route behaviour, cable distances, codecs — and is confirmed in writing on the quotation. Where the honest answer is that a fact is not held, this site says so.

No competitor models, specifications or prices — none are held, so none are printed
No vendor is disparaged anywhere on this site, and no judgement about another vendor's equipment is made or implied
The trademark notice below names the relationship plainly: NEXVIA is not affiliated with, endorsed by or sponsored by the vendors named
Published figures are confirmed on the quotation, not asserted from memory

Frequently asked questions

Do you publish a comparison against NEC systems?

No. This site holds no NEC models, specifications or prices, so none are published and no comparative claim is made about the vendor. This page is an assessment instead: what to inventory in a small or mid-size office, what to decide at each step and what the published figures of the replacement equipment are. The comparison that matters is against your own installation.

What is the smallest sensible system for a small office?

It depends on the trunk and analog counts. The OM20G is the one-box option: 24 SIP trunks, up to 4 analog ports ordered as 4 FXS, 4 FXO or a 2+2 mix, 16 GB of internal storage, extension numbering from 200, and the only model in the range that can dial out over a 3G/4G USB modem. Tell us the extension and line counts and we will confirm the model rather than guess upward.

Can the existing extension numbers be kept?

Yes, in the plan. Numbering on the new system starts at 200 and can follow the scheme in use, so staff keep the numbers they know; a 500-entry route table handles number translation and directed routing where the schemes differ. Published numbers are bound so that a dialled number lands on the right extension or group, and number portability itself is a carrier process coordinated with your carrier.

What happens to the analog lines and the analog phones?

They can both stay. Analog lines are kept on FXO ports and act as the escape route: an outbound call over a SIP trunk that times out or returns a 4xx/5xx/6xx response is routed out over the analog line instead. Analog telephones stay through the GA10 (2 SIP lines, 1 FXS port) or through analog ports on the PBX — up to 4, 12, 48 or 96 depending on the model. Fax machines keep working as T.38 or G.711 pass-through.

Can we reuse the existing cabling?

Where the cable is a working data run, yes: a PoE desk phone needs one cable, and integrated PoE is published on the X303P/G/W and X301P/G. Where a position has only a two-core pair, the PN1 carries network and power over it — up to 1600 m for the network function without power — and the PN8 and PN24 switches carry 8 and 24 two-wire devices at up to 300 m for network plus power, with X303-2 Wire and H1-2 Wire as the endpoints at the far end.

Can the old and the new system run together while we change over?

Yes. A phone that publishes several SIP accounts — the catalogue runs from 2 to 20 SIP lines depending on the model — can hold registrations on both systems while its block is being moved, so a changeover can be one window or a phased sequence with both dial plans answering in between. We confirm the per-model arrangement before the plan depends on it.

Do you supply the phones and the phone system?

Yes. NEXVIA is a system integrator: we design the system, supply the equipment, commission it on site and support it afterwards. That can be desk phones on an existing platform, or a complete design around an IP PBX with the analog ports, wireless handsets, door stations and paging sized to the site. All equipment is supplied under the NEXVIA brand. Commercial terms are quoted per site.

Relationship and trademark notice

NEXVIA manufactures its own range of IP telephony equipment — PBX systems, SIP phones, hotel handsets, nurse call, intercom and public address — and integrates it for the site: design, manufacture, supply, commissioning and after-sales support.

This page is a migration assessment written from public, verifiable information: the published figures of the equipment NEXVIA supplies. It publishes no competitor model numbers, specifications or prices, and it makes no comparative or disparaging claim about another vendor. What to assess is decided by your own inventory and requirements.

All trademarks named on this page — including Avaya, Cisco, Mitel and NEC — are the property of their respective owners. NEXVIA is not affiliated with, endorsed by or sponsored by those vendors. A vendor name is used only to identify the system a buyer may be planning to change from; it is not a statement about that vendor's products.

nec alternative · nec pbx replacement · migrate from nec · nec to sip · nec phone system replacement

Page author: NEXVIA EngineeringPublished:2026-09-29Last updated:2026-10-13

Covers: nec alternative · nec pbx replacement · migrate from nec · nec to sip · nec phone system replacement

Equipment on this page is supplied and integrated by NEXVIA; no competitor specifications or prices are published on this site.

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