Moving from Analog PBX to IP PBX: A Practical Plan

The old analog PBX in many offices still works, just barely. Every extension is a copper pair in a cabinet, adding a new hire needs a technician, nothing is recorded, and nobody can take a client's call away from their desk. Then an extension card dies and there is no replacement on the market.

Moving to an IP PBX fixes this, provided the move is planned: outside lines, phones, network and system size. Here is how to plan it, with numbers you can work from.

What an IP PBX actually changes

An IP PBX is an appliance or software that handles calls over your data network using SIP. An extension is no longer a copper pair but an account that an IP phone, mobile app or PC softphone registers to. Phones plug into the same switches as the computers, so moving someone to another office means moving the phone.

• Full web management: add an extension or change call routing in minutes.
• IVR, call recording, queues, voicemail and conferencing come built in.
• Branches call each other as internal extensions over the internet.
• Staff keep their own extension when working from home or on site.

The best-known names in this class are the Grandstream UCM series and the Yeastar P-Series. We stock Grandstream IP PBX systems and Yeastar IP PBX systems in several sizes.

Outside lines: SIP trunks or landlines on FXO

A SIP trunk delivers voice over the internet or a provider link, carrying several simultaneous calls on one connection. It is the cleanest option technically, but availability and terms vary by provider and area.

In Egypt, plenty of companies still run on analog landlines and won't give up numbers their customers know. That is what FXO ports are for: an FXO port accepts a landline from the public exchange. Many IP PBXs have FXO ports built in, and when you need more, an FXO gateway converts the lines to SIP. One landline on one FXO port carries one call at a time, so five lines means five simultaneous outside calls, no more.

FXS is the opposite: it powers an analog device such as an old phone or a fax. Yeastar FXS gateways let you keep existing analog phones in the warehouse or reception during the transition. GSM/4G gateways can also add mobile SIM cards as outside lines.

IP phones, PoE and mobile apps

IP phones are usually powered over the network cable with 802.3af PoE, so no socket or adapter per desk, and one UPS in the network room keeps every phone alive. Most desk phones draw a few watts, but plan on about 6.5 W each unless the datasheet says otherwise. 40 phones × 6.5 W = 260 W, so choose a switch with at least that PoE budget plus margin. TP-Link smart managed switches also give you the VLAN and QoS features you will need.

Fanvil IP phones and Grandstream IP phones range from basic staff handsets to colour-screen models with BLF keys for reception. Field sales and technicians can skip the desk phone: a softphone app such as Grandstream Wave (for UCM) or Linkus (for Yeastar) rings their extension on their mobile.

Extensions, IVR, recording and queues

Start with a numbering plan: 1xx admin, 2xx sales, 3xx support, 9 for an outside line. Keep the IVR short, three or four options at most, with a separate after-hours message. Queues spread incoming calls across available agents and play hold music instead of a busy tone.

For recording, a mono G.711 WAV file takes about 0.48 MB per minute. Recording 300 minutes a day over 26 working days comes to roughly 3.7 GB a month, so size storage for the retention period you need.

Sizing: users and concurrent calls

Three numbers drive the choice: users, concurrent calls, and FXO ports or SIP channels. As a starting estimate, assume 20 to 25% of users are on outside calls at peak, more for sales teams and call centres.

Example: 40 staff means 8 to 10 concurrent outside calls at peak, so 8 to 10 landlines on FXO, or a mix of landlines and SIP trunk channels. For calls crossing the internet (branches, remote staff), bandwidth per call and direction is:

Figures assume 20 ms packets with IP, UDP, RTP and Ethernet headers, needed both upstream and downstream. Then pick a model with clear headroom on users and concurrent calls for growth.

Network requirements: VLAN and QoS

Voice is more sensitive to delay and jitter than any other traffic. A large upload on a flat network can break calls.

• Voice VLAN for the phones, which LLDP-MED can assign automatically on switches that support it.
• QoS marking voice as DSCP 46 (EF) and prioritising it on switches and the router.
• Targets: one-way delay under 150 ms, jitter under 30 ms, packet loss under 1%.

Most IP phones have a second port for the PC, so one existing network point can serve both, with the voice VLAN tag keeping traffic separate. Test old cabling first, though. Auto provisioning on Grandstream UCM and Yeastar systems can push extension settings to compatible phones, which saves hours of manual setup on a 40-phone rollout.

Common mistakes

1. SIP port 5060 open to the internet with weak extension passwords. That invites toll fraud. Use strong passwords, restrict allowed IPs and turn on automatic blocking.
2. SIP ALG left on in the internet router, a frequent cause of one-way audio and calls dropping after a few seconds.
3. No UPS: when power drops, the PBX and PoE switch go down with every phone.
4. A flat network without VLAN or QoS, followed by complaints about choppy audio.
5. Moving everyone in one day without a pilot.

Our advice: move one department first and keep the old PBX running in parallel for a week. You can link the two systems temporarily through FXO and FXS ports so both groups can still call each other, then migrate the rest once quality is proven and users are trained.

How Do Link helps

Do Link for Security Systems supplies Grandstream UCM and Yeastar IP PBXs, Fanvil and Grandstream phones and VoIP gateways, along with switches and UPS units from APC/Schneider and Delta. Everything is original with a one-year warranty, and our technical team helps you size the system before purchase and supports you during commissioning. Companies and contractors get wholesale and project pricing, with delivery to all governorates in 2 to 3 working days. See our PBX and telephony solutions.

Tell us your headcount, current landlines and branches, and we will propose the PBX, phones and switch. Get in touch through our contact page, on WhatsApp at 01098280784, or at our Bab El Louk branches, open daily 10 AM to 10 PM.

Recommended products from Do Link

Yeastar P570 IP PBX, 300 Users (up to 500), 2x E1/T1/J1 ReadyP570Grandstream GXW4248 V2 48-Port FXS Analog Gateway (V2)GXW4248 V2Yeastar P560 IP PBX, 100 Users (up to 200), E1/T1/J1 ReadyP560Yeastar TA3200 32-Port FXS VoIP Gateway, 2x RJ21TA3200

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