Industry · Call centres and BPOs
Voice connectivity for call centres and BPOs
High-volume calling depends on capacity that holds at peak, outbound settings that match your dialler, and controls that stop unexpected usage. We plan each of these with your operations and technical teams before live traffic moves.
- Sized for peak concurrency
- Dialler-aware limits
- Per-client number pools
Operational needs
What a high-volume voice operation needs from its trunks
Call centres and BPOs run several client programmes on one platform, often with very different traffic patterns. The trunk configuration has to reflect that.
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Concurrent capacity for peaks
Channels are sized to the busiest interval of the busiest day, not the average. Campaign launches, seasonal peaks and new client programmes are planned in advance so capacity is in place before the traffic arrives.
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Inbound queues
Client programmes often share one platform. Each inbound number is delivered to your PBX or dialler with the dialled number intact, so the platform can place the call in the correct client queue.
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Number pools
Pools of local or national numbers can be assigned per client or per campaign, used for inbound lines and, where you are authorised to present them, as outbound caller ID.
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Predictable routing
Routing rules for each number, number format and caller ID handling are written down on the configuration sheet, so agents, supervisors and your clients know exactly where each call goes.
Outbound calling
Outbound calling and dialler considerations
Diallers can start far more calls per second than a human team. Trunk settings and dialler settings must be agreed together.
Channel and call rate limits
A predictive dialler may place several calls for each available agent. Your channel count therefore depends on the dialling ratio as well as the number of seats. We agree a channel limit and a call rate limit (new calls per second) that match your dialler, so a misconfigured campaign cannot exhaust capacity or generate unexpected cost.
Caller ID you are authorised to present
Your platform can present numbers you hold or are authorised to use, for example a client’s number under a written agreement. Many networks and regulators now check caller ID more closely, and calls presenting numbers the caller is not entitled to use may be blocked or flagged. Presenting a recognisable, valid number also helps answer rates.
Local rules on outbound and telemarketing calls
Countries regulate outbound and telemarketing calls differently, covering matters such as permitted calling hours, do-not-call registers, consent, abandoned-call limits and recorded messages. You are responsible for following the rules that apply to your campaigns and to each destination you call.
Fraud controls and failover
Controls that limit risk on high-volume trunks
A compromised dialler or PBX can generate expensive traffic within hours. These controls are agreed during setup and reviewed when campaigns change.
Fraud and usage controls for call centre trunks
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Channel limit
- What it does
- Caps the number of simultaneous calls on the trunk or per sub-account
- Agreed during setup
- Limit per trunk, and per client programme where needed
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Call rate limit
- What it does
- Restricts how many new calls can start per second, which protects against runaway dialler settings
- Agreed during setup
- A rate that matches your dialler configuration
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Destination restrictions
- What it does
- Only the countries and number types your campaigns need are enabled
- Agreed during setup
- Enabled destinations; premium-rate closed by default
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Usage alerts
- What it does
- Notifies named contacts when traffic or spend moves outside the expected pattern, where available
- Agreed during setup
- Thresholds and alert recipients
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IP allow-list
- What it does
- Accepts traffic only from your dialler or PBX public addresses
- Agreed during setup
- Your public IP addresses
Inbound failover
If your platform or site becomes unreachable, inbound calls can be sent to an alternate destination, such as a second site, a backup platform or an overflow partner. The destination and the order are agreed and tested.
Outbound resilience
Outbound calling depends on your platform reaching the trunk. A second internet connection, a second site or a secondary trunk configured on the dialler keeps campaigns running if the primary path fails.
Sizing guidance
How to size channels and bandwidth
Use real interval data from your current platform where you have it. Forecasts are acceptable for a new programme, with a review after the first weeks.
- Take the busiest 15- or 30-minute interval from your call reports, inbound and outbound combined.
- For inbound queues, convert busy-hour traffic into Erlangs and use Erlang B (or Erlang C for queue staffing) to find the channels needed at your target blocking rate.
- For outbound, multiply the agents on predictive campaigns by the dialling ratio, then add the channels used by connected calls and transfers.
- Add headroom for growth and for campaigns that overlap.
- Size bandwidth at roughly 90–100 kbps per G.711 call in each direction, including overhead. One hundred concurrent calls need about 10 Mbps each way, before any other traffic.
Our guide to estimating SIP channel requirements works through the method in more detail.
Onboarding
How a call centre is onboarded
Moving a live operation is planned so that no client programme loses service during the change.
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Step 1: Traffic profile
Agent seats, peak concurrent calls, inbound and outbound mix, destinations and the dialler or PBX platform you use.
Input: call reports or forecasts
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Step 2: Caller ID and numbers
Numbers to port or order per client, and the caller IDs each campaign will present, with evidence that you are authorised to use them.
Output: number plan
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Step 3: Controls agreed
Channel and call rate limits, destination restrictions and alert thresholds are set to match the campaigns.
Output: configuration sheet
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Step 4: Load and failover tests
Test calls in both directions, DTMF, caller ID presentation and the failover route, at a scale agreed with your team.
Output: test results
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Step 5: Phased go-live
Traffic moves one client programme or campaign at a time, with live calls reviewed before the next is moved.
Output: go-live review
Recommended services
Services call centres usually combine
SIP Trunking
Concurrent channels for your dialler or PBX, with call rate limits, destination controls and failover.
Explore SIP Trunking
Virtual Numbers
Local, national and toll-free numbers per client or campaign, ported or newly provisioned.
Explore Virtual Numbers
Cloud PBX
A hosted system with queues and IVR for smaller teams or new programmes without their own platform.
Explore Cloud PBXFAQ
Questions from call centre teams
Can we present our clients’ numbers as caller ID?
Only where you are authorised to use them and the rules in the destination country allow it. We may ask for evidence of authorisation, such as a letter from the number holder. Presenting numbers you are not entitled to use is not permitted.
Do you support predictive and progressive diallers?
Standards-based diallers that place calls over SIP can usually connect. We review the platform, its call rate settings and how it handles answer detection and abandoned calls before go-live, and set trunk limits that match.
How quickly can capacity be increased for a new campaign?
Channel limits are a configuration change, but larger increases may need a check of routes and your network. Tell us about planned campaigns early; the timing is confirmed for each request.
Can traffic for each client be kept separate?
Where needed, separate trunks or sub-accounts can be set up per client programme, each with its own numbers, limits and call records. This simplifies reconciliation and client reporting.
Next step
Plan capacity and controls for your call centre
Share your traffic profile and platform details. We will reply with a proposed channel plan, the controls we recommend and an itemised quote.
Helpful to include
- Dialler or PBX platform and version
- Agent seats and peak concurrent calls per programme
- Dialling ratio on predictive campaigns
- Outbound destinations and caller IDs to present
- Numbers to port or order per client