Kenwood TM-251A Instruction Manual page 117

Frequency step
The size of frequency change produced by turning the
Tuning control one position or pressing the microphone
[UP] or [DWN] button one time while in VFO mode.
Full Duplex
Full Duplex mode allows simultaneous transmit and
receive communication using the Main Band for
transmitting and the Sub-band for receiving.
Group code
When using Page, a group will commonly agree on a
single code that will be used for calls targeted for all
members. This code is the Group code. See "Station
code".
Hang Time
See Squelch Hang Time.
Keypad
The collection of keys on the microphone used to send
DTMF tones.
110
Locked-out channel
An electronically marked memory channel that will be
skipped during Memory Scan.
This is a quick way to
configure your Memory Scan without actually erasing
data from memory channels that you may want to keep.
Main Band
Memory channel
A "storage" location where you record an operating
frequency and many other associated parameters for
quick recall later. Normally, all commonly used
frequencies including those of local repeaters would be
saved in memory channels to eliminate manually
selecting frequently-used frequencies.
Memory Recall
A function that fetches a previously saved operating
frequency and associated data.
See "Memory channel".
Memory Scan
A function that monitors sequentially all programmed
memory channels that are not locked-out.
See "Scan".