An office phone system with a call menu and ring groups: how one Muscat office routes its calls

How one Muscat office answers its phones

At Ruby Shipping Line's new Muscat office, we installed an office phone system with a call menu (IVR), five ring groups for the departments, eleven SIP phones and outbound calling on the company's lines. Those four parts are the heart of an office phone system, and each one answers a question about a call: what the caller hears first, which phones ring, where the call is picked up, and how staff call out. The rest of that job is in the case study of Ruby Shipping Line's office.

A company's call flow is its own business, so this post does not reproduce that office's menu. It explains the building blocks behind it and the decisions you make for each one, so you can plan the same thing for your own office.

The parts: an IP PBX, extensions and SIP phones

The phone systems we install sit in the customer's office and belong to the business. A PBX, short for private branch exchange, is an office's own switchboard. It gives each desk an extension, connects internal calls, and passes outside calls in and out over the company's lines. An IP PBX does that work in software, over the office network rather than dedicated phone wiring.

The desk phones speak SIP. RFC 3261, the standard that defines the Session Initiation Protocol, describes it as a signalling protocol for creating, changing and ending sessions, Internet telephone calls among them. SIP handles the ringing, the answering and the hanging up. The voice itself travels as a stream of small packets using RTP, the real-time transport protocol set out in RFC 3550.

When a SIP phone starts up, it registers with the PBX. In RFC 3261's terms, registration binds an address to the device where it can be reached right now, so the PBX knows which phone on the network is extension 104 and rings it when someone dials 104. A person who moves desks keeps their extension: the phone, or its settings, moves with them, and nobody rewires anything.

Plan the extension numbers in a pattern people can remember, such as one range per department, and give each ring group a number of its own. The phones plug into the office network just as computers do, and desk phones can take their power over the same cable, so every desk with a phone needs a network point. That makes the business network setup part of the phone job: voice needs priority on the network, and enough upload capacity for the calls you make at the same time.

Outside calls arrive on lines or SIP trunks that the business rents from a licensed operator such as Omantel or Ooredoo. A SIP trunk delivers phone lines over a data connection. The lines and numbers stay on the business's own account with its operator, and staff call out on those same company lines.

The call menu: what an IVR does and how to design one

IVR stands for interactive voice response. It is the recorded greeting that answers a call and lets the caller choose where to go by pressing a key. Sangoma's IVR Module User Guide, written for its own PBX software, gives the familiar example, "press 1 for sales and press 2 for the company directory", and notes that an option can open a sub-menu. Its advice on size is plain: no more than five or six options in a single menu, and single-digit choices only. It also suggests waiting 4 or 5 seconds for the caller to press a key.

Our own advice for a menu that callers get through without trouble:

• Use fewer options than the limit. Three or four choices are easier to hold in mind than six.
• Put the most common reason for calling first, and name each option the way callers think ("bookings", "invoices and payments"), not after internal team names.
• Give callers a way to a person. A key such as 0 should ring reception or an operator group, so a caller whose question fits no option still reaches someone.
• Decide where silence goes. Some callers press nothing, or press a key that leads nowhere. The guide's settings include a timeout destination and an invalid destination for exactly these cases, so point both at a person rather than a dead end.
• Record the greeting in Arabic and English, and keep it short. Let callers choose a language first, or say each option in both. The menu can also let callers who know an extension dial it directly.

Ring groups and hunt order: who picks up

A ring group is one number that rings several extensions. The same vendor's Ring Groups Module User Guide lists several ring strategies, and three are worth knowing:

• Ring all: every available phone in the group rings at the same time until someone answers. It is the default in that guide, and it suits a team where anyone can take the call.
• Hunt: the available extensions ring in turn, one at a time. You decide who comes first, so it suits a team with a lead person and a backup.
• Memory hunt: the first extension rings, then the first and second together, then the first three, and so on, so the call widens until someone takes it.

Two settings matter as much as the strategy. The first is ring time, how long the phones ring. For hunt-style strategies the guide applies it to each step, so five people at 20 seconds each can mean up to 100 seconds of ringing before anything else happens. The second is the destination if no answer: where the call goes once the ring time runs out. The guide notes that this is most often an extension or a general voicemail box. Set one for every group, so that no call simply rings out.

After hours, holidays and voicemail

The same system decides what happens outside working hours. That vendor's Time Conditions User Guide describes a rule with two destinations, one for calls that match a set of times and one for calls that do not, and notes that it is often used to route calls differently during business hours and after them. In practice you set:

• the working days and hours, and a lunch break if the office closes for one;
• a rule for public holidays, with a named person who updates the dates each year;
• what an after-hours caller hears: your opening hours, and a voicemail box for a message.

The guide also describes an override that switches the rule by hand, which helps on a day the office closes early.

Voicemail catches the calls nobody answers, in working hours or out of them, and the message can arrive in your email as a recording you can play back. Decide which boxes you need: one for each person who needs one, and a shared box for each department or for after hours, each with someone who checks it every morning. A shared box that nobody owns is where messages sit unheard.

What to decide before the install

The hardware is the easy part. The routing comes from decisions only you can make, so bring answers to these questions to the first meeting:

• Departments: which teams take outside calls, who belongs to each, and whether each group should ring all at once or hunt in order.
• The menu: the options and their order, their wording in Arabic and English, the key that reaches a person, and where silence goes.
• Hours: working days and times, breaks, holidays, and what callers hear when you are closed.
• Voicemail: which boxes, who checks each one, and which email address receives the recordings.
• Phones: how many desk phones, where each one sits, and a network point at every one of those desks.
• Lines: how many calls you take at the same time, and which lines or SIP trunks you rent from your operator today, or need to order from it.

Our business phone systems page lists Setup from 150 OMR, and we quote your office after learning how calls reach you today. If you are moving off old phone lines, moving your business phones to VoIP covers the switch itself.

Before the system goes live, test it the way a caller would. Ring the main number from a mobile, try every option, wait without pressing anything, call after hours and leave a voicemail, then check that the recording arrives where it should.