In 1965, Drake introduced the matching T-4X transmitter and R-4 receiver. The "4-Line" twins satisfied a desire for high performance, operational flexibility and a set of features not possible to squeeze into the TR-4's small size. The matching units used the same PTO technology as the TR-4, and were capable of transceive operation using either the receiver's or the transmitter's PTO to control the operating frequency. Drake introduced the T-4 "reciter" which was a transmitter add on for the R4 series receivers (it had no PTO of its own and used the PTO and other signals from the R4 receiver to generate the transmit signal), making them a two piece "transceiver", but it saw limited sales and is a rare item on the used ham gear lists these days.