Most likely you were hearing the phone company. Most of the NWS TX's are remotely located from the forecast office, and rely on telephone circuits to connect between them. These are usually provided (for a hefty fee) by the local phone companies. Sometimes they use UHF radio links, or ride microwave circuits, etc. The phone company will use audio test sets that generate that obnoxious tone to allow for troubleshooting. The tech's trying to fix the circuit and easily identify when they are listening to the correct pair of wires (or other circuit device), when they hear the tone. Sounds like they got the circuit running but had not taken the tone off the line yet. Since the WX Transmitters are keyed all the time, they just pass on what they hear from the phone circuit. It's a dedicated circuit only connecting between the two locations, full time (no dialing, etc.).
