D-Link DPH-70L IP Phone

This device lets you call international locations from a local landline via VoIP. All you need is a dial-up ISP connection and a VoIP calling account

Thursday, July 20, 2006

This newly launched IP phone from D-Link allows you to make ISD calls, at far cheaper rates than the regular PSTN networks. Earlier, this used
to be achieved from a computer via software like Net2Phone, but now you're no longer dependant on a computer for the job. It doubles as a regular PSTN phone and is quite easy to set up. You just need a dial-up ISP connection and a VoIP calling account (calling card coupon). Using its menu button, you can configure the dial-up Internet account and calling card details in the phone (we received a Rs 500 calling card coupon from IPYantra for testing this phone). To start the call, dial your ISP by pressing VoIP button. Once connected, it appears in VoIP mode. 

You can now start making international calls. The LCD display shows the status of your calls. The phone offers hands free operation with an adjustable speaker and ringer volume control. In addition, it has silence suppression, voice activity detection and comfort noise generation features, which ensure voice quality at both ends. 

It supports both H.323 and SIP protocols. Plus, it uses a V.34 Modem interface using V.90 Data pump. For voice compression, the unit uses G.723.1 and G.729A/AB compression. These are the latest compression technologies being used for VoIP based communication.

Performance and call pricing
We tested this device by calling the US, the UK and Singapore and checked for distortion, echo, quality of voice and delay. We also compared the cost of VoIP calls with those made from PSTN networks. The PSTN networks used were those of BSNL and Airtel. We found that calls made from the VoIP and Airtel networks were much cheaper than BSNL (see table), but qualitywise the BSNL network performed better. In VoIP calls, there were some nagging quality related issues. For example, when we made calls to the UK, there was distortion, echo and delay in voice quality.

To confirm this, we made calls of the same duration from a PSTN network, and found it to be free of these problems. The same thing happened when we made calls to Singapore. However, calls to the US, gave us good voice quality across both VoIP and PSTN networks. To cross check, we did the same test three to four times and every time we got a different performance. VoIP calls are therefore, totally dependant on your Internet connectivity. Because of the dial-up connection, you never know the speed at which you will be connected to the ISP.

Bottom Line: This is a good option if you need to make lots of casual or quick phone calls abroad. It's not suitable nor is it meant for business users, as its quality is not as reliable as that of a PSTN based network.

Sanjay Majumder

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