Sennheiser evolution wireless series EM 100 Instruction Manual page 45

Synchronizing transmitters with receivers
44
If you want to use the frequency bank "U":
Make sure to use receivers from the same frequency range (see page 5
and the type plates of the devices).
Only use frequencies that are approved and legal in your country.
On one of the receivers, select a channel within the frequency bank "U"
(see page 39).
Assign this channel one of the receiving frequencies (see page 39).
Synchronize a transmitter with the receiver (see page 20).
OR
Manually set the transmitter to the same channel and frequency that
you set on the receiver.
Repeat for the remaining transmitters and receivers as described
above.