The DVA-2WA is only compatible with a “carbon” handset for recording.  On most carbon handsets, the mouthpiece and receiver covers are round and you could unscrew the covers, like the plain old telephones (2500 sets).  Handsets with another type of transmitter (rather than carbon) will provide either no playback at all or extremely low volume playback.  We sell a compatible handset under part number Q171030 and they are $39.00.  A microphone can also be used to record if that would be easier (like the NRG Research part number SA-25).