The Singing Machine SMM-112 Instruction Manual page 5

Troubleshooting
b) Have you plugged your headset microphone into the transmitter input
jack?
c) Does the Transmitter contain one (1) 9-volt battery?
d) Are the Microphone Volume and Master Volume controls of your Singing
Machine set to a high enough level?
e) Does the Receiver contain one (1) 9-volt battery, is it properly connected
to your Singing Machine, and is it turned on?
CAUTION: Two of same microphones should not be used in same location
unless with one wireless and one wired microphone.
Wireless Microphone Information
This device complies with Part 15 of the FCC Rules. Operation is subject to
the following two conditions:
(1) this device may not cause harmful interference, and
(2) this device must accept any interference received, including
interference that may cause undesired operation.
The term IC: before the radio certification number only signifies that " "
Industry Canada technical specifications were met.
Warning: Changes or modifications to this unit not expressly approved by
the party responsible for compliance could void the user's authority to
operate the equipment.
E4