What are CLIP and CLIR and how do they work?
CLIP (Calling Line Identification Presentation) and CLIR (Calling Line Identification Restriction) are two supplementary telephone services that determine whether the called party sees the caller's number.
CLIP ensures that the caller's number is displayed on the recipient's phone screen. CLIR Conversely, this display suppresses the caller's number: the recipient will see text such as "number hidden" or "private number". Both functions are part of the signalling transmitted along with the call via the telephone network or SIP protocol.
How to use CLIP and CLIR in practice?
For the company, correct CLIP configuration is crucial: the customer sees that a specific company is calling, not an unknown number. This significantly increases the likelihood of the call being answered.
- Company number on outgoing calls - a salesperson calls from a mobile phone, but the customer sees the company's landline number (via FMC or softphone).
- Branch number - each department displays its own DID number on outgoing calls
- CLIR for specific lines - anonymous hotline for internal purposes or the HR department
- Compliance with legislation - only a number verified by the operator as your own can be displayed
CLIP and CLIR in the Virtual Central Station
In the cloud-based central system, you can set which number is displayed for outgoing calls, separately for each line or group. Note: presenting another person's number (a number you do not own) is prohibited by the Electronic Communications Act, and operators filter such calls using anti-spoofing measures.
If customers report seeing a different number during call-back than the one they originally called, the cause is usually an incorrectly configured CLIP in the central system or on the SIP trunk. On virtualni-ustredna.cz, CLIP is set individually for each line via a clear dashboard.
Frequently Asked Questions
Can a company hide its number (activate CLIR)?
Technically yes, but consider the impact: a hidden number reduces the likelihood of the customer answering the call. CLIR makes more sense for specific internal lines, not for outgoing business communication.
What is anti-spoofing and how does it affect me?
Anti-spoofing is a protection that prevents the display of a number not owned by the caller. Operators block such calls or flag them as suspicious. Therefore, it is necessary to have CLIP set to a number you actually own.