Sennheiser TCI 01 Instructions For Use Manual page 6

Overview
The TCI 01 Telephone Controlling Interface
is an additional device for the digital wireless systems of
Sennheiser Communications.
makes it more convenient to make or receive calls since
you no longer need to lift off the telephone's handset. A
call is accepted or ended simply by pressing the wireless
system's hook button.
is operated either with a mechanical handset lifter or
with a telephone featuring an AEI or DHSG interface.
When used with the TCI 01, telephones featuring an AEI
or DHSG interface do no longer require a mechanical
handset lifter.
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