iMSO-204 Probes Digital Recording Module

DUT: RadioShack Digital Record/Replay Module

In the setup pictured above, Oscium’s iMSO-204 digital oscilloscope measures two analog waveforms on Radio Shack’s digital recording module. The module, part number 276-1323, uses a single IC to record and playback up to 20 seconds of voice or other audio. Plotted on the iPad Air display are the VCC for the chip and the voltage at the chip’s output for driving the speaker.

See The Module In Action

This 30 second video clip shows Oscium’s iMSO-204 measuring the voltage across the speaker leads when the module replays a bit of whistling.


Breaking Down Radio Shack Digital Record/Playback Module

The Good

Just add 9 Volts. In the day and age of “some assembly required” it’s a refreshing change to get something ready to use right out of the box. This little module works as advertised. All you need to do is supply it with (approximately) 9 Volts. The onboard regulator accepts a wide range of input voltages and regulates down to 5 Volts for the IC, microphone and speaker.

Easy to use and abuse. The open-faced module is assembled with radial leaded, thru-hole components. If someone wanted to change component values or add elements to the design, this module makes that experimentation easy. It would also be easy to remove parts of this assembly and use them in other circuits; kind of like reusing and recycling.

The Bad

No drive. As built, the module has some minor drawbacks. Most noticeable is the poor microphone sensitivity. The instructions suggest that the microphone be placed 2 to 3 inches away from the audio source. The other weak point is the lack of power for really driving a speaker. Considering the whole thing comes fully assembled for less than $12, be prepared to make a few concessions.

The Blob. The most frustrating part of studying this module is the giant blob of epoxy covering the record/playback IC. All other components and connections are accessible for probing and analysis, or for experimentation through value changes and component swaps. The next blog on this module will take a close look at an IC that performs all the functions as the chip under the blob. Once you understand the circuit and it’s capabilities, this would be a fun circuit to modify and tailor to specific applications.

What Comes Next

In the next series of blog posts, we look at some of the different functional blocks that make up RadioShack’s Digital Record/Playback module.

  • Part 1: Record & Replay Circuit Analysis
  • Part 2: LDO Regulator Circuit Analysis
  • Part 3: Microphone Circuit Analysis
  • Part 4: Speaker Circuit Analysis

Datasheets and Downloads

RadioShack's one page for the 276-1323 Digital Record/Playback Module.

RadioShack's folio user's guide for the 276-1323 Digital Record/Playback Module.

Oscium's handheld oscilloscope is now available with universal platform support! So, if you're interested in using the scope on iOS, Android, PC or Mac, Oscium supports you. Please go to iMSO-204x for more information.