It is not recommended to use multiple pairs of DW 20T and DW 20R because of possible interference. We have tested 2x DW 20T senders (T), each one sending to 2x different DW 20R (R) devices in parallel in different rooms 200mm apart and it worked. Although the test was successful on a small scale, we cannot give any guarantees, as factors such as environment, local situation interference and other wireless units in close proximity such as routers, smartphones, etc. may cause the signal to drop-out. For this reason, if you choose to attempt this you do so at your own risk as this is not officially supported.