Digital Message Repeater


Exhibit Control Engineering has developed an economical series of DMR players.  The first thing to go in our strategy to reduce costs was the metal enclosure.  Our DMRs are bare circuit boards.  We envisioned that they would be located in either an exhibit structure/kiosk or installed in an electronic rack, both of which provide protection for the electronics, eliminating the expense of a metal enclosure.  The second strategy for reducing cost was to provide a number of versions of DMRs so the user isn’t buying capability they don’t need.


The circuits and quality for all the DMRs are the same, only the method of control varies in each version of the Basic DMR.  They play stereo mp3 files copied onto flash memory cards.  Any version can either provide unbalanced line level audio or can have a 15W per channel amplified speaker level audio.

There are two basic types of control: serial and switch.  With either type of control the following features can be provided:  play one of 254 files; stop file playing; mute and un-mute both channels of audio; volume up or down;  pause; resume and set and clear loop mode.  Volume up and down can be accomplished by either up and down button controls or via a potentiometer.  In the serial control mode you can also poll the player for its status and current volume.  Serial control is via a very simple protocol that uses not more than two bytes of data.

For those DMRs that are controlled via switches (buttons), our DMR has a feature we don’t believe is available on any other DMR:  we can provide feedback for each button.  We can provide a current sink of up to 500ma at 30vdc for each button input.  This is enough power pass-through to illuminate LEDs, power 12vdc lamps or trigger larger power relays to control light boxes or other binary electronic devices. Most commonly, they are used to activate LEDs in the illuminated buttons:  all buttons are on when no audio (or the attract audio) is playing and then when a button is pressed to play its audio, it remains illuminated while the other button indicators are extinguished.  Other scenarios could be specified for light boxes or other designs.

The amplifier circuit can easily provide 15 watts per channel.  The circuit can actually provide up to 38 watts per channel.  The challenge to obtaining the higher level of audio is providing an adequate sized heat sink (which we can provide) and finding a power supply that can provide the needed juice without inducing noise.  We can provide a power supply for the 15W versions at additional cost but are still looking for a suitable, more powerful supply for the greater audio outputs above 15W.

Below is a video demo of one of our DMRs that not only plays audio but also controls a 3-digit, 7-segment display appropriate for an interactive kayak exhibit.

Click on the one of the group images below to see more information on the different variants of this product.  Or, click on this link to download a brochure on this product line:  Basic DMR Brochure

 Serial DMR Amp

Looping DMR

Serially Controlled DMR

Basic DMR 4-B,4IO wamp DMR-8Inputs

DMR w/4 Inputs & 4 IOs

DMR w/8 Inputs & 8 IOs

Basic DMR 15-B,15IO wAmp Basic DMR 30-B,30O wAmp

DMR w/15 Inputs & 15 IOs

DMR w/30 Inputs and 30 IOs