ki4moc said:
Hello,
When a Motorola repeater is keyed up before the repeater dropped from the previous conversation, it will transmit a two tone chirp (medium tone and a high tone)..then followed by MDC. Could it possibly be a warning tone?
Anyone have any info.....thanks
What you described sounds like tone remote keying from a comparator to the repeater. It serves the purpose of remotely activating the transmitter. That configuration is used commonly in analog radio systems. The keying sequence command is 2175/ 1950 Hz, but with very high gain, the high tone actually comes out sounding like it's lower because of distortion through filtering (2175 Hz is filtered by a sharp notch filter because it is also used to keep the transmitter keyed). If the gain is turned down a little, it starts sounding like a high/ low tone burst again.
Anyway, tone remote keying is not exclusive to Motorola. The signaling format is an industry standard and a Motorola, GE, RCA or Daniels base can be keyed by any number of devices that work with the format. So, no warning tone.
Warning tones, etc. may be popular in the ham radio world, but in public safety, when a message needs to get through, nobody wants to hear courtesy tones. The MDC is just part of what the mobile users have enabled on their radios.
