Check the listing for details. LINEAR AMPLIFIER RELAY KEYING BOX. Color: Beige, Condition: New. Listed at 35.99 USD. For sale , this home made Relay Control Box to be use to key your linear amplifier.It is recommended to use this device to activate in transmission mode your liner amplifier and to prevent damage on your transceiver. Will only work with amplifiers that requires a connection to ground to activate TX mode. With this device your transceiver will be completely isolated from your linear amplifier.Each unit is tested prior shipping and you have one year warranty ...to honor warranty you must submit your original order detail.Have one of this myself using a FT-747GX and a Dentron GLA-1000...been working with no issues for the last 5 years. SpecificationsInput voltage 10 to 13.8 Vdc at 50 maMax switching current 5 AMax switching voltage 250Vac -30VdcClosure speed 15 millisecond Connections12Vdc ..................................connect to 12 or 13.8Vdc output on your transceiver ...or to your main power supply.Transceiver PTT ..................connect to your PTT output on your transceiver.Amp Relay............................connect to the "Relay" input or "Key" input in your Amplifier This item is made to order and WILL TAKE 5 DAYS TO SHIP.....will ship USPS priority mail.