SIP
You can make voice calls over the internet using your own smartphone using an app such as Groundwire. You can also use other types of device if it supports the SIP protocol, or even connect in your own app via SIP.
Smartphone apps
There are many apps available for iOS and Android that support SIP. The one we recommend is Groundwire because although it has a one-off cost, it is the most reliable app we've seen by far.
Other apps do work, but many have problems with reliability, battery drain, and call quality.
Required settings
All SIP devices need these settings to connect to our network.
| Option | Value |
|---|---|
| Server | sip.emf.camp (Using the IP is not supported) |
| Username | Your number |
| Password | The SIP password displayed in your number's setup page |
Optional settings
Some devices may also require some of the settings below. If in doubt, just fill in the required settings and see if it works.
| Option | Value |
|---|---|
| Transport | UDP |
| Port | 5060 |
| TLS | No |
| SRTP | No |
| Display Name | The name that appears when you call someone from this number |
| Auth ID | Your number |
| STUN | Disabled |
| Keepalive | Yes (SIP OPTIONS, 30 second interval) |
Codec Settings
A “codec” (coder-decoder) is the method used to digitise and compress audio before sending it over the internet.
If your SIP device needs you to configure codec settings, we recommend enabling the following codecs in this order of preference.
| Codec | Quality* | Notes |
|---|---|---|
| OPUS | High quality (HD voice) | Best for WiFi / Mobile |
| G722 | High quality (HD voice) | Widely supported |
| G711 A / A-law / PCMA | Standard quality | Widely supported traditional telephony codec |
| G711 U / μ-law / PCMU | Standard quality | Widely supported traditional telephony codec |
| GSM / AMR | Standard quality | Used on mobile phone networks |
| T.38 | Standard quality | Improves fax machine reliability |
* High quality "HD Voice" is only available when both devices on the call support the same codec.
Security
VoIP devices are an attractive target to hackers, bots, and other bad actors.
- Don’t connect a VoIP device directly to the internet, protect it behind a router / firewall.
- If you’re running a SIP server like Asterisk make sure it’s adequately secured with a firewall, complex passwords etc.