What is synthetic call monitoring
Synthetic call monitoring is a robot that calls your 0800 number, your IVR or your SIP trunk on a schedule, the way a customer would, and records what happened: whether the call connected, what answered and how the audio sounded. It answers the question no equipment dashboard answers: can a customer reach the company right now?
Summary
- A synthetic call is a test call placed by a system, not a person, on a schedule and always the same way.
- It measures what the customer experiences: the call connects, the right IVR answers, audio flows both ways and the voice quality is good.
- Passive monitoring analyzes the real calls that already happened; synthetic monitoring also sees the hour when nobody called.
- To count as a measurement the call has to be real: a PBX that is powered on and a registered trunk do not prove that a call connects.
- In Monitor by 2N5, each voice circuit gets a test call every 15 minutes by default, and only four failures in a row open an incident.
What is synthetic call monitoring?
Synthetic call monitoring is the practice of deliberately calling, from a system and on a schedule, the numbers customers dial, and recording the result of each call. The call is “synthetic” because a robot places it, not a customer; it is real because it travels through the carrier’s network for real, the same way a customer’s call does.
Each test call follows a fixed script: dial the number, wait for the answer, listen to what answers, compare it with what should answer and hang up. What gets recorded is what matters to the people who run the telephony: whether the call connected, how quickly, with which SIP code, and how the voice sounded.
What is a test call for?
Every hour, or every fifteen minutes, it answers one question: could a customer reach the company right now? The PBX and trunk dashboards answer another question, whether the equipment is up, and the two answers can differ.
| What happened | What the PBX dashboard shows | What the test call shows |
|---|---|---|
| The carrier stopped routing the 0800 to the trunk | All green, no calls | The call does not connect, with the SIP code returned |
| The IVR was swapped or the platform published a faulty flow | All green, calls answered | The greeting heard does not match the reference recording |
| The carrier answers with a “number does not exist” message | No calls | The call connects, but the message is not the IVR’s |
| The call connects, but audio goes one way only | Normal call | Missing or weak audio in the measurement |
| Voice quality dropped on the route | No alarm | MOS-LQO below the limit |
An 0800 that spends the night down without anyone noticing is the classic case. The guide Your 0800 went down and nobody told you walks through a night hour by hour.
How does a synthetic call work?
In four steps, repeated on each circuit’s schedule:
- Call. The system dials the monitored number (0800, 0300, 4004, a landline number or a SIP trunk number) from outside the customer’s network.
- Listen. It records whether the call connected, the SIP code and Q.850 cause returned, and the audio received.
- Compare. It checks what answered against the IVR reference recording and measures the voice quality of the audio received, the MOS-LQO.
- Decide. An isolated failure is retried; only consecutive failures become an incident and an alert.
The last step is what separates useful monitoring from a false-alarm generator. At Monitor by 2N5’s default pace, each circuit gets a call every 15 minutes. When one fails, the call is repeated three times, 2 minutes apart; four failures in a row, the first and three retests, open the incident, and two good calls in a row confirm the recovery. The guide Line-down alerts, without false alarms describes that path.
How is it different from passive monitoring?
Passive monitoring watches the real calls that cross the network, by capturing traffic, and computes indicators about them. Synthetic monitoring places calls on its own. The practical consequence is simple: passive monitoring only sees what happened when there was a call, and at night, on a weekend or on a rarely dialed number there may be none.
The two complement each other, and neither replaces the other. The guide Passive monitoring vs active test calls compares them and says when each one fits.
What does a synthetic call not see?
It sees what happens from the origin it calls from. A failure that only affects customers of one mobile carrier, or one region, can go unnoticed if the test call leaves from another path; the guide Why an 0800 won’t connect from a mobile phone covers that case. It also does not replace analyzing real calls to find the cause inside your own network.
Which terms show up with the topic?
People who search for it find “test call”, “active monitoring” and “availability test” in Portuguese, and “synthetic calls” and “synthetic voice monitoring” in English. They are the same concept. What changes from tool to tool is what it calls (just the number, the whole IVR, the SIP trunk), where it calls from and what it does with the result.
How does Monitor by 2N5 do it?
Monitor by 2N5 is a managed service: 2N5 registers each circuit, records the IVR reference greeting, sets the schedule and places calls from Brazil to 0800 numbers, IVRs and SIP trunks. Each call becomes a record with time, number called, SIP code, Q.850 cause and MOS-LQO, and the set becomes the SLA report for the month and the last 12 months. See how it works and 0800 and IVR monitoring.
Frequently asked questions
What is a synthetic call?
It is a test call started by a system, on a schedule, that follows the same script every time: dial a number, listen to who answers, sometimes press an IVR option and hang up. The result of each call is recorded with its time, SIP code, Q.850 cause and audio assessment, and becomes the basis of the measured availability.
Is synthetic monitoring the same as active monitoring?
In telephony, in practice, yes. Both terms describe tests the monitoring system starts itself, as opposed to passive monitoring, which only observes the calls customers already made. Synthetic is the name used in website and network monitoring, and active is the name more common among people who work with VoIP.
Why use synthetic calls if I already monitor the PBX?
PBX monitoring shows the equipment from the inside. A synthetic call shows the whole path from the outside, from the carrier to the answer. A broken carrier route, a faulty number portability change or a swapped IVR leave the PBX all green, because no call reaches it. Only a call from outside sees that.
Do synthetic calls get in the way of my trunk channels?
Hardly at all. Each test call takes up a channel for a few seconds, and Monitor works within an agreed call limit so it does not compete with your customers for channels. The default frequency is one call every 15 minutes per circuit, which comes to 96 short calls a day.
How often should synthetic calls run?
The shorter the interval, the less time an outage goes unseen. At 15 minutes, an outage is seen within 15 minutes and confirmed 6 minutes later by the retests. For a 99.9% monthly target, which tolerates 43 minutes, a test once an hour is too little.