The lowest frequency is called the lower limit and the highest frequency is called the upper limit. These limits are often stored in two specific memory locations. PTT - Push To Talk. This is the key used to cause the radio to transmit. To restart with the default features, functions and data.
Most modern radios utilize a microprocessor.
Resetting the microprocessor will often clear all memory and VFO data. Reverse - see Offset, Duplex and Check. The Reverse key will cause the Transmit and receive frequencies to be exchanged. The radio will the receive on the repeater input and transmit on the repeater output. The control that shifts the receiver up or down in frequency to improve the reception.