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Product Reviews
 January 2002



DSG Technology, Inc.
20265 Valley Blvd, #N
Walnut, CA 91789
Tel: 909-595-8908
Fax: 909-595-5508

Price: MSRP is $299 for the InterPhone. DSG�s VoIP products and services can be purchased through their online shops; for further information, e-mail may be sent to [email protected]

Installation: 5
Documentation: 2.5
Features: 3.0
GUI: 3.0
Overall: B

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.

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.

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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