Using one of the BeHear headsets on its own in Personal Hearing mode will pick up sound from the television and amplify it according to your hearing profile (if you have performed the Hearing Assessment in our W&H BeHear app to personalize the device). This may be sufficient for your needs.
However, the benefit of the HearLink (or HearLink PLUS) transmitter is that it captures the TV audio and transmits it directly to the personalized headset, eliminating distractions (such as room reverberation, and ambient noise).
Additionally, since your headset can pair simultaneously with two Bluetooth devices, if you receive a phone call on your paired mobile phone while watching television the TV audio will be muted automatically, and then resume once you disconnect the call.