Reset gateway to factory default and ensure you are running the latest firmware.
Review vendor documentation and assign a IP / Subnet mask / default router or gateway / DNS entries to the device. Ensure you are documenting all this with notes and screenshots for eventual publication as an FAQ.
Disable any automatic firmware upgrades to ensure the device remains on the tested firmware.
After having created the gateway (and its ports within 3CX using the Generic Gateway template) you will need to add the ports to the gateway.
Follow vendor documentation to find out where the port entries must be made.
Typically the port settings will require Channel number / Authentication ID / Authentication Password. The Authentication ID and Authentication Password can be left to the defaults suggested by 3CX.
Ask the Telecoms company for their expected DTMF signaling lengths and volume
Ask the Telecoms company for the mechanism they use to send the Caller ID. There are various standards and can vary.
Set PSTN fax to T38 settings to allow a maximum speed of 9600bps if testing FAX capabilities for the gateway.
Check Polarity reversal requirements with your Telecoms company.
Recommended Codec priority should be set to G711U / G711A / G729 / GSM for Voice calls.
Recommended codec for fax is T38 as primary codec and maximum allowed speed should be 9600. Other codecs are NOT supported for FAX interaction.
Set RTP Packet time to 20ms.
Set DTMF options to RFC2833 as this is the most reliable for PSTN gateways.
Testing of gateway once configured
Check registration settings and ensure device registers for each configured port.
Ensure default registration time is set to 900 (or the closest value to this as possible).
Make an inbound call to the phone – ensure 2-way audio.
Make an inbound call to the phone and place caller on hold – ensure Music On Hold (MOH) is heard
Resume call – ensure 2-way audio
Make an attended transfer of an inbound call – ensure caller hears MOH, and caller is successfully transferred including 2-way audio.
Make a blind transfer of an inbound call – ensure caller hears MOH, and caller is successfully transferred including 2-way audio.
Ensure outbound Caller ID appears as expected.
Ensure inbound Caller ID appears as expected.
Make inbound call to a DR and ensure all MOH, audio are heard as expected.
Making an inbound call to a DR, test all DTMF tones from 0-9 and ensure they are accepted correctly, predictably.
Making an outbound call to some Auto Attendant/DR service, test all DTMF tones from 0-9 and ensure they are accepted correctly, predictably.
Receive an inbound call through the gateway and divert this through the PBX to an outside number, exiting via the same entry device. NOTE: This is not a valid/necessary test in the case of a single-FXO gateway device.