... than 3 seconds. Auto research launch signal then lock, no string frequency and anti-interference ability is strong. ... 7. Application: multimedia room,technique room,classroom and report hall.8. Transmitter to select from 1090 and ... must pay return postage for any return reason, no exception. In return, we will pay the postage ... be given. Please Noted: We do not cover any items for damage after use or as ...