By adding Remote Radio Control DTMF activation to a fully automated crossing you would provide train crews the ability to request the activation of the crossing prior to occupying any of the circuits. Adding DTMF to a fully automated crossing would not be a safety concern because the crossing would still operate as described above if the train crew were to forget to DTMF the crossing.
In a remote DTMF activated crossing warning system the crossing is activated by a DTMF radio code as the train approaches the crossing. Because the train crews are responsible for activating the crossing no approach track circuits are provided with the system. In remote activated crossing the train crew is responsible putting the gates in the down position. The approach to the crossing is replaced with remote DTMF radio control.
DTMF Stands for Dual Tone Multiple Frequencies. DTMF are the tones you hear when you dial a telephone. A code is programed in the DTMF decoder and the DTMF Decode listens for the specific programed code. Once the correct DTMF code is received and decoded an output will be provided. This output is then used as an input into the system for a specific command. In the case of a DTMF activated crossing this DTMF output would be used as an input to activate the crossing.