Motorola PM1200 User Manual page 29

Radio Firmware Features
9.2.2.2 DPL Decode
Receive DPL is used in detection of a sub-audible code that is used in
the unmuting rules of the radio.
If DPL is selected, the radio will receive digital private line code on the
selected conventional personality. The DPL code determines which
code the conventional personality will attempt to decode.
9.2.3 Inverted DPL
Inverted DPL inverts Digital Private Line (DPL) signals when they are
received by the radio. Inverted coding allows more traffic/usage on
frequencies.
If DPL Invert is enabled on the transmit radio but not on the receive
radio, then the receive radio will not unmute.
If DPL Invert is enabled on the receive radio but not on the transmit
radio, then the receive radio will not unmute.
If DPL Invert is enabled on both the receive radio and the transmit
radio, then the receive radio will unmute.
The encode and decode operation of this Inverted DPL should be
similar to DPL except all the bits in the DPL code are inverted in the
DPL operating process.
9.3 TPL Reverse Burst
This feature is used to transmit a Tone Private Line (TPL) code at the
end of a transmission - once the PTT button is released, and while
operating on the current Conventional Personality. This sub-audible
tone causes the receiving radio to mute its speaker before loss of a
carrier is detected. Muting the speaker eliminates unwanted noise
(squelch tail) during loss of carrier detection.
If the TPL Reverse Burst is programmed to standard or non-standard
via the CPS, a Tone Private Line (TPL) shut-off code will be
transmitted at the end of a transmission once the PTT button is
released, on the current Conventional Personality.
PM1200 Mobile Radio with Control Head 17