How To Identify ESI Phone Features

Posted by Jeff Csisar on


ESI phones come in several variations, more than most other phone system brands. Luckily, all ESI part numbers include their features right in the part number. This makes it easy for us to know what a phone can do.

DFP vs. IPFP – The Big Difference

The largest difference when it comes to the newer ESI phones is DFP vs IPFP. DFP stands for Digital Feature Phone. DFP phones run over traditional RJ-11 phone cords and are used with ESI digital line cards. These phones are powered through the phone system and feature more traditional phone programming and set up.

IPFP phones by contrast stand for Internet Protocol Feature Phone. IPFP phones run over your network, and are newer, VoIP based technology. IP feature phones, as their name implies, receive an IP from your network and are provisioned and configured based on this IP from your phone system.

What is right for you is generally based on the system you already have. Do you run a VoIP based phone system or a more traditional digital type layout? The system you currently run will generally dictate the phones you choose.


24 Key vs. 48 Keys – Functionality and Programming

The ESI phones come in three size variations, the 12 key, 24 key, and 48 key. The 12 key is rare, and not widely used so it will not be discussed here. The 24 key and 48 keys are two different sized phones with different programming capabilities. The 24 key is the smaller phone, and it comes with less programmable keys. The 24 Key phones can support up to 12 custom feature keys while the slightly larger 48 key phones can handle 30 programmable functions! The large disparity for little increase in price and size make the 48 key phone the most popular ESI phone sold.


H, FD, TAPI, RMT – What Do They All Mean?

In addition to DFP/IPFP and 24 Key/48 Key options, there are additional extra features that can commonly be found on ESI phones. Each of these options is outlined below:

H - H is the most common feature you’ll see on an ESI phone. It stands for headset port. All H DFP phones (the most common type) include a headset port for plugging a headset right into the phone.

FD - FD is better known and Full Duplex. Full duplex is a type of speakerphone technology that allows for better conference phone calls.

TAPI - Short for Telephony Application Programming Interface is an API which enables PCs running Windows to use telephone services. TAPI is designed to allow for control of your phone through a computer.

RMT - RMT is unique in that it only applies to IPFP phones. RMT is short for Remote, and this feature allows IPFP phones to connect to phone systems on the Wide Area Network (WAN). Normally, IPFP phones are limited to LAN connections (IPFP2 phones come with the RMT feature built in, so all IPFP2 phones are RMT).


With all this knowledge, we hope you can find the right ESI phone for you. If you still have any questions, please feel free to contact at 1-800-95-REFURB or by email at

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