A slave test unit is used in conjunction with a remote test unit to test voice signal quality parameters, such as clarity, delay and echo. A remote master test unit, or a remote slave test unit, controls the slave test unit via commands sent by the remote test unit over a phone connection established by the remote test unit. Such a system of test units eliminates the need for a human test operator to be present at the location of the slave test unit. The inclusion of a "dialback" capability in the slave test unit allows a remote test unit to instruct the slave test unit to call back the remote test unit, thus allowing voice quality tests to be performed over a phone connection that has been initiated by the slave test unit. This capability is advantageous in voice quality testing over phone connections involving a digital data network, since the path of the connection through a data network is typically determined by the location of the origination of the call.