From: j.albert@snet.net

On 4/21/14 11:33 PM, mroberds@att.net wrote:
>   I can
> sometimes hear six DTMF tones on the same channel they use for voice,
> at about the time that one of the trains should be arriving.  Sometimes
> these six tones are shortly followed by one single-frequency tone.  Are
> these tones possibly operating the switches at the siding?

Chances are the tones you're hearing are (for lack of a
better word) "hailing" tones. Used either by the train crew
to "summon up" the dispatcher's radio and "cue it in" to the
right location (near you), or it could be coming from the
dispatcher's radio, indicating that he is on the line and
ready to communicate.

If there's a control point involved, the power-operated
switches are almost certainly being controlled from the
dispatcher's office over a "land line" based CTC system.

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