Overview of the new DECT IP phone Grandstream DP750 / DP720

Grandstream has a long and fairly successful release of almost the full range of equipment for IP telephony, working under the SIP protocol. In this case, the main bet is placed on the budget segment, which is more than relevant for our market at the moment. Therefore, it is not surprising that Grandstream VoIP equipment is popular in Russia and customers increasingly choose their products from this particular manufacturer. Last week, the Grandstream DP750 DECT IP Phone went on sale and we, as Grandstream official dealers, could not miss this event and not get to know the device closer.

A bit of history

The first attempt of the Grandstream company in the production of DECT IP phones using the SIP protocol can be considered the DP715 model released in 2012. The de facto standard in this class of devices is the ability to connect several handsets to one base station at once, with each of them assigning their own SIP account. The main differences between phones from different manufacturers are mainly reduced to the number of supported handsets and simultaneous calls within one base station. And of course, the functional characteristics of the tubes themselves, which actually have to deal with end users.

If everything was pretty dull with the DP715 (monochrome display, not the most convenient keys, controversial design), then the base station's support of five handsets and four simultaneous conversations significantly compensated for this drawback. For comparison, competing solutions from Panasonic and Gigaset allowed no more than three and two simultaneous conversations, respectively, and the Yealink W52P with the characteristics similar to the Grandstream DP715 was and is significantly more expensive. The ability to organize a fairly low cost wireless communication in a small office by connecting inexpensive and fairly unpretentious handsets to one base station provided the Grandstream DP715 with a certain popularity.
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The new DECT IP phone Grandstream DP750 / DP720 is positioned not just as an improved version of the old model, but as a phone of another - higher - class. The more interesting it will be to evaluate the novelty in comparison, both with the previous model, and with DECT IP phones of other manufacturers.

Grandstream DP750 Base Station

It emphasizes the positioning and packing of the phone, or rather two packs at once - the DP750 base station is supplied separately, the Grandstream DP720 handset is not included in the kit and is sold as a separate device. Such a solution is more typical of multi-cell DECT IP systems, where it looks absolutely logical. In the case of the DP750, this is more like a marketing ploy. It is difficult to come up with another explanation for this decision, especially since at the moment no other handsets except the DP720 are supported by the base station. That is, the user will have to buy at least one handset anyway, why it was not included in the package, as all other manufacturers do, is not entirely clear.


Be that as it may, the concept laid down in the previous model DP715, where the base station is combined with a charging glass, the manufacturer decided to give up. And for this it is worth saying thank you to him. If before you had to choose from two evils - to pull the power cable to the user's workplace or the user to run to the charging glass - then you can simply throw the new base station to any convenient place, closer to the network and the electrical outlet. The second, by the way, is not necessary at all - the DP750 also supports power over PoE. For those who are not happy owners of PoE-switches, there is a power connector, made in the form of a fashionable now micro-USB. In addition to it and the only network port, the base station has no more connectors. No PSTN-ports are provided by the manufacturer - the DP750 is positioned, first of all, as a telephone for office use. The only button on the base station (in addition to the recessed reset button) performs two functions: long press switches on the handset registration mode, short - helps to find already registered handsets using a paging call.

Cordless tube Grandstream DP720

The charging cup from the delivery set of the DP720 no longer performs any auxiliary functions and is therefore compact. Connectors for mounting on the wall, unlike the base station, it is not provided, but the power connector - all the same micro-USB.


A first look at the new handset is enough to understand - in terms of ergonomics, a big step forward has been made in comparison with the DP715. The handset has become wider, thicker and substantially less rounded - thanks to this “brick” form factor, the phone is very confident in the hand. The keyboard also became more ergonomic - the keys slightly increased in size and got rid of rounding. Because of this, as well as a wider body, it became easier to hit the right keys.

The new handset is not only comfortable, but also beautiful - black matte plastic in its lower part looks stylish, especially in combination with the thin white font, which has the key signatures. The display edging, on the other hand, is glossy, like all recent Grandstream IP phones. In this case, beauty really requires sacrifice - any contact with your finger or ear leaves a noticeable trace on the glossy frame.

The display of the DP720 is color, 1.8-inch diagonal and 128x160 pixels - the Yealink W52P and Panasonic KX-TGP600 have exactly the same. As for the implementation of the graphical interface, compared to the Panasonic, our today's hero looks much more advantageous. For the most part, this is the “merit” of Japanese designers, who for some reason decided to use only a small part of the 65,000 colors provided to them, and also chose not very nice icons and fonts. But in comparison with the Yealink W52P, the new device is clearly losing - in order to get the same stylish and thoughtful graphical interface, Grandstream engineers still have to work hard. However, the DP720 does not cause any rejection - again, in comparison with the monochrome display of the previous model DP715, this is a huge step forward.

Also in the Grandstream DP720 handset it is worth highlighting the presence of two useful connectors - firstly, this is a full 3.5mm jack for connecting a headset, and secondly, the next micro-USB port for charging the handset without using a glass.

Work with multiple handsets

Let's move from purely visual sensations to the main characteristics for each DECT IP phone. So, the Grandstream DP750 base station supports five wireless handsets, which so far only the Grandstream DP720 can act as. It is a pity that the manufacturer did not provide support for the tubes of the previous generation Grandstream DP715 (at least at the level of basic telephone functions), not to mention the handsets of other manufacturers that fully work on CAT-iq technology.

The second important characteristic of the DECT IP base station is the number of simultaneous conversations supported. In the case of the DP750, it is limited to four, which in most cases is enough for five handsets. Some manufacturers share the number of supported simultaneous calls for the broadband and narrowband modes and, as a rule, a larger number naturally indicates in the marketing materials. For example, the Panasonic KX-TGP600 supports eight simultaneous calls using narrowband codecs and four using wideband codec G.722. In the case of the DP750, there is no such separation - in all modes, four conversations within the base station are supported.

Another characteristic of the base station that should be noted is the number of independent SIP accounts. It is clear that they should be at least not less than the number of supported handsets. In the case of the Grandstream DP750, there are exactly twice as many, that is, ten. However, there are no restrictions on the distribution of accounts between the handsets. That is, you can assign one tube at least all 10 accounts and vice versa - the same account - five tubes. In the second case, the incoming call will be processed in accordance with the logic selected by the user - only one specific handset rings, all the tubes are simultaneously or in turns. In the same case, when several accounts are assigned to the same handset, the user has the opportunity to choose from which of them to make another call. But do not forget that one handset cannot receive more than two simultaneous calls (one active, the second on hold), regardless of the number of accounts assigned to it. Perhaps this is a limitation for the benefit - it is difficult to operate with a large number of simultaneous calls on a landline phone, not to mention DECT handsets, which have less screen and number of keys.

For clarity, the spoiler shows a label that summarizes all the basic characteristics of base stations for the most popular DECT IP phones.

Sound quality

Another difference Grandstream DP750 from the previous model DP715 is to support full HD-sound. In truth, for some time the DP715 was the only popular DECT IP phone model without the support of the G.722 wideband codec. However, in 2015, the codec was added by the developers with the proviso that anyway you should not expect full HD-sound from the phone due to the physical limitations of the speaker and the microphone of the handset.

Is it really so easy to check by comparing the DP715 with a new phone, in which the sound quality is presented as one of the advantages. Objectively speaking, when using a wideband codec with both handsets, differences in the quality of receiving / transmitting audio are not easy to notice. The sound is quite clear on both phones, it is very comfortable to talk in this mode. When using narrowband codecs, the sound loses somewhat in volume, but only slightly, it affects the comfort level minimally.

Approximately the same picture is observed in comparison with other popular models of DECT IP phones. The differences in the quality of the sound reproduced by them are much less noticeable than the differences between the used codecs with the same tube. In principle, this is a logical consequence of the unification of modern production, when devices from different manufacturers consist essentially of the same components.

I would also like to draw your attention to the fact that the Grandstream DP750, in addition to supporting all standard codecs for speech coding, also supports free Opus audio format, which is notable for its flexibility, as well as an excellent ratio of sound quality to introduced delays.

Autonomous work

Offline time was the Achilles heel of the Grandstream DP715. Some users had to hear that a full battery charge was enough for just a few tens of minutes of conversation, despite the fact that the claimed standby time for this handset is 10 hours. All the fault was the use of conventional nickel-metal hydride batteries. As a rule, many of them came to the end users completely discharged and with a residual capacity of not more than 20-30%. Considering that their initial capacity was only 500 mAh, it is not surprising that sometimes they did not last long enough.

Grandstream made the right conclusions from the mistakes of the past, equipping the new phone with low-discharge nickel-metal hydride batteries (LSD NiMH) with a capacity of 800 mAh. According to the manufacturers, this type of battery is able to save from 70% to 85% charge after a year of storage at a temperature of 20 degrees, and after three years of storage, their capacity can reach up to 97% nominal.


In addition to using modern batteries, the ECO mode function is also responsible for long battery life. It not only extinguishes the screen of the phone during inactivity, but also constantly adjusts the signal level of the handset, depending on the RSSI value and error rate. For this reason, we did not check the battery life stated by the manufacturer - 250 hours in standby mode and 20 hours in talk mode - since it largely depends on the remoteness of the base station.

Instead, we simulated the usual work of the phone in office conditions: put the base station in one corner of the office, the handset in the other, and took it off on Monday morning. After 5 days, quite active use of the phone on Friday evening showed up more than half the charge. This is really an impressive result!

In the spoiler, a comparative tablet with the stated battery life of various DECT IP phones.

Radius of action

The stated range of the Grandstream DP750 is absolutely standard - 50 meters indoors and 300 meters outside. These are the usual numbers for the vast majority of modern DECT phones. However, some of the first users of the new device noted that the DP750 and DP720 pair have a striking radius of coverage in comparison with competitors.

We, unfortunately, could not confirm such optimistic forecasts - all five DECT IP phones that we had on hand (Grandstream DP750 and DP715, Panasonic KX-TGP600, Yealink W52P and Gigaset C530A IP) showed almost identical results - up to several meters, both indoors, and on open space.

As for the declared values, it is also very careful to focus on them. The radius of action on the street is in principle not a very useful parameter for an office DECT IP phone. And the radius of action in the room obviously depends on many parameters, in particular on the location, thickness and material of the walls and partitions. However, according to the sensations, the declared figures of all modern DECT IP phones are rather somewhat overestimated than vice versa. Therefore, the most optimal and realistic scenario for the use of such devices is the following: one base station is bought in the office, at which pipes of the office staff are recorded.

Perhaps that is why Grandstream, unlike most competitors, does not release devices such as repeaters for its DECT IP phones. Indeed, when used in an office, their value is not very great - for small premises, they are usually not required, and in large offices with a large number of employees it is more logical to use multi-cell IP DECT systems.

Impressions of work

Despite the obvious advantages of DECT IP phones in comparison with stationary ones, they also have significant drawbacks. The compact dimensions of the handset do not allow placing any function keys on it, which makes working with the phone less convenient. For example, on a fixed IP phone, most daily operations such as hold, switch between calls, transfer, enable do not disturb, mute the microphone, select a line, and others are usually performed with one touch. When working with a cordless handset, to perform most of the functions, you have to go into the menu every time.

However, as amended above, there are no obvious complaints about working with the DP720. Perhaps the only exception is making a call transfer with notification (accompanying transfer) - too many actions need to be done for this, and their order is not obvious. But perfectly implemented work with two or more accounts - when you press the hardware call button, the call goes through the main account (it is set in the menu), and for manual line selection, use the context-sensitive call key instead of the hardware one. Another plus is the presence of separate speaker and mute keys. Sometimes they are combined with the lower keys of the dialer - and this is not very convenient.

What else is striking, or rather in the ears, when working with the phone - these are ringtones. Firstly, there are quite a few of them and some of them are too funny for the corporate environment, and secondly, the loading of their own melodies has not yet been implemented.

By the way, working with the DP720 sometimes causes pleasant nostalgia for the pre-smartphone era, and cheerful polyphonic melodies are just one of the reasons. They can also include the keypad lock by long pressing the # key, and turning on the silent mode - by holding the * key. About the work without recharging for a week has already been said above. And how convenient it was to assign speed dialing of the number of parents, friends, girls to each number key of your mobile phone. Also in DP720, it's a pity that you only need to save the dialed number to the phone book first.

By the way, there are six phone books, and all of them are stored at the DP750 base station. Five of them are private; they are assigned to each handset separately, the sixth book is common to all handsets. You can import a shared phonebook from XML at a time, you can set up scheduled imports using HTTP, HTTPS and TFTP, or you can synchronize with the LDAP directory.

The phone supports 27 languages, including Russian. Russified as a phone menu, and Web-interface.

Brief summary

To say that the Grandstream DP750 / DP720 has made some kind of bright, powerful impression is to bend one's heart. You can really praise the new phone for the amazing battery life of the handset and its stylish design. But the DP750 / DP720 doesn’t have any serious flaws - all functions work properly, it’s convenient to use the phone, it’s nice to talk on it. In general, Grandstream has got another high-quality IP phone, which has noticeably surpassed its predecessor. True and in the price of a new device significantly "recovered." If earlier the DP715 (base kit and handset) could be purchased for $ 80, then the estimated retail price of the DP750 base station is $ 74 and about $ 70 more will have to be paid for the DP720 wireless handset.