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Founded in 1997, DSG Technology, an Internet telephony network company, merged with sister company DSB Technology in 1999. With a new focus on VoIP end-user hardware, DSG Technology, Inc., commenced with production of Internet telephony products such as the InterPBX, IPStar, and the subject of this TMC Labs product review: The InterPhone. The InterPhone is a standalone hybrid phone capable of making pure IP calls and IP-to-PSTN calls through the use of their gateways and a JustDialIt account � DSG�s ITSP. In addition, it�s also a POTS telephone.
All DSG-brand products are based on their company philosophy and
underlying framework called InterPhoneWork, which instills identical
underlying design, functionality, and a unique operating dialect in each
product. DSG says that InterPhoneWork provides an optimal framework for
Internet telephony by enabling seamless integration between DSG telephony
devices and various applications including networks and disparate network
backbones.
Linking PSTN networks to the IP world are approximately one hundred of
DSG�s IP 200 gateways; tied together via the Internet they form the
JustDialIt ITSP network. JustDialIt�s gateways provide the underlying
switching that makes phone-to-phone, device-to-phone, and phone-to-device
services possible to its user base.
The InterPhone utilizes DSG�s own communication protocol, employing the
G.711, G.723.1, and G.729 audio compression codecs and echo cancellation.
The device has 2 MB internal RAM and 8MB flash memory, upgradeable software,
and is equipped with an LCD display and menu buttons for on-board device
configuration. TelNet can also be used to access the InterPhone utilizing a
TCP/IP connection. The unit is DHCP compliant, while the hardware employs
two Ethernet ports for purposes of connecting an additional device. Nine
function keys, 21 programmable keys and speakerphone are also standard
features.
TMC Labs acquired a set of two DSG InterPhones through Washington-based
reseller CTDepot.com. We set up the
phones in the Lab for testing over our LAN, while additionally utilizing
JustDialIt to test IP-to-PSTN and PSTN-to-IP capability, along with our
standard battery of tests: installation, ease-of-use, voice quality, and
overall product performance is also noted.
Setting up the phones was very simple, and provisioning for DHCP made it
even simpler. The connection of a phone consisted of linking a RJ-45 cable,
a power cable, and RJ-11 phone wire. If the DHCP service isn�t available,
the device requires manually entering a static IP, IP gateway, and subnet
mask. This is all done through the LCD display and three configuration
buttons under the display. Since the phone is TelNet compliant, we connect
and make a few changes � everything seemed to function as it should.
Connection and addressing were the essential tasks required to get the
phone online. Depending upon the mode of operation either an @ symbol or a
telephone icon should be a constant on the LCD indicating that the phone is
receiving the correct information from its respective connection. The phone
reseller will probably handle the ITSP account and initial programming of
account numbers � as CTDepot.com did with our phones.
Utilizing the PSTN-to-phone functionality, or the device ID dialing
method on our LAN (behind a firewall) created a problem for us. Even with
the correct ports open, we still experienced network address translation
(NAT) issues. As a result, we couldn�t receive (or transmit) the required
packets to and from the outside world, which in turn, generated various
error messages on the InterPhone�s LCD. The only other issue we had during
set up occurred after connecting the RJ-11 wire. Shortly after connection we
received a �fast-busy� tone. A quick tour through the System Setup
portion of the menu revealed that the PSTN flash time was set at 600ms.
Adjusting it to 400ms rectified the issue.
TMC Labs is a proponent for interoperability on many levels. Usually when
testing IP phones such as the InterPhone, we immediately opt to set up some
different products employing the same ITU standard (an H.323 device to
NetMeeting, call for example) as a part of our test bed. However, since the
InterPhone uses a proprietary protocol, our usual testing configuration wasn�t
an option. Instead we acquired a second InterPhone and tested IP-to-PSTN,
PSTN-to-IP, IP-to-IP, and LAN calling configurations.
IP-to-IP calling is one of the primary features of this phone, that is,
as long as the person you�re trying to reach is using an InterPhone too.
DSG�s proprietary protocol prevents the InterPhone from communication with
other non-DSG devices via IP. Calling another InterPhone can be achieved
either through dialing the other party�s IP address, or by utilizing
another InterPhone�s device ID. Using the device ID is more convenient for
two main reasons: It is only six digits as opposed to 12, and it never
changes. In the long run this allows for a more reliable, simpler procedure
for end users � as they are never required to verify their own IP address.
Though the phone�s signaling protocol operates over TCP/IP networks
just fine, we couldn�t utilize DSG�s device ID service behind our
firewall. Since our InterPhones couldn�t exchange information with the DSG
servers, and the phones don�t handle this processing themselves, we had to
�dial� the internal IP of the other phone to contact it. Both phones
were less than ten feet from one another in the Lab and connected almost
instantly with very, very minimal latency on our LAN.
All that is required to dial a PSTN number from the InterPhone (in IP
mode) is the dialing of the number one wishes to call. Simply pecking the
keys on the keypad including the country and area code (even if it�s a
local call) and the phone does the rest. The overall quality was good. The
first three to five seconds of the call (when the translation of codecs is
taking place) are not as clear as the rest of the call. After those initial
seconds, the calls were clear, with minimal latency.
Even though it wasn�t our intent to focus on the JustDialIt ITSP within
this review, it�s difficult to avoid since the InterPhone depends on the
ITSP for IP to PSTN calls. It is however, also possible for a regular POTS
user to reach an InterPhone in IP mode, given that the correct information
is shared between parties at some point prior to the call: JustDialIt
account holders are required to relinquish their ten-digit pin number, a
local gateway phone number, and the InterPhone device ID number as their
contact information, should someone want to call them via PSTN to IP.
Additionally, the JustDialIt network will also connect two PSTN users over
its network in much the same fashion: By dialing the local gateway number, a
ten-digit pin number, and the regular phone number (including area and
country code) The advantage to entering the required thirty digits (give or
take a few) is in skirting local bell or long-distance carrier charges for a
lower VoIP rate. The InterPhone could not be used with an ITSP other than
JustDialIt at the time of testing.
ROOM FOR IMPROVEMENT
Aside from the proprietary signaling protocol used in conjunction with
the InterPhone, there were several other things TMC Labs would have done
differently. A Web interface would have really been a nice addition. As
simple and user-friendly as the LCD is, scrolling through a compact,
on-board display to change system properties just isn�t any fun �
especially when it�s not illuminated nor backlit. In any event it is no
competition for a full-screen browser that displays all options at the same
time. On both the IP and PSTN sides of the product, ANI and caller ID
service functionality would have been another plus. Although DSG is already
housing information and software on their servers that translates IP
addresses into device ID numbers to simplify calling, we wonder: How about
appending a name to the number? Basic PSTN Caller ID and caller ID services
support would have also been good features for the PSTN side of the phone.
CONCLUSION
DSG�s InterPhone with v. 3.41 software has very a usable and intuitive
overall design, with the dual functionality of an IP phone and a standard
PSTN telephone. While in our experience the call quality was high, DSG�s
proprietary signaling protocol was not interoperable with other non-DSG IP
communications devices (and other ITU standards) at the time of testing.
However, DSG representatives did inform TMC Labs that the next version of
InterPhone�s software will employ SIP compatibility. We look forward to
testing that version, as well.
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