Comes with everything you see in the picture, both TX and RX and the relay board.
This kit is a 2-channel version of Kit QK180, our 4-channel UHF Remote Control kit. We have simply removed two of the 4 channels from Kit 180 and used a 2-button Transmitter unit, QA17TX. Up to 15 Transmitter units can be learned by one RxQA17RX unit.
Press button 1 (the small button) while simultaneously pressing the LEARN tact switch on the main board. You only have to do this briefly for under a second. But note it takes about 15 seconds for the two units - the TX and the RX - to connect and recognize each other. During this 15 seconds it seems that one and only one keypress of the Tx unit ill be recognized. Just disregard this. Wait the full 15 seconds until the two units have connected. Do not press the LEARN button again. Just wait 15 seconds. Note the VALID DATA LED comes on when you press the tact switch. Tx units attached to any Rx unit can be unattached by pressing the LEARN button continuously for 8 seconds. The VALID DATA LED is on during these 8 seconds. As soon as the LED goes off then you know that all Tx units previously recognized by the Rx unit have now been unattached from the Rx unit. Two of the 4 relay positions in kit 180 are removed.
QK157 PCB Dimensions: 84 x 61mm (3 5/16 x 2 3/8)