Hi Dave, The systems we've worked on in aviation follow a standard EIA tone format which is probably similar to yours. On depressing the PTT bar on the handset, the encoder transmits a guard tone burst of 2175 Hz at a high level followed by one of several possible?function tone bursts known as F1, F2, and so on. They're at?100 Hz increments (2050 Hz, 1950 Hz, 1850 Hz, etc.). Then a 2175 Hz tone is sent as long as the PTT bar is depressed, but 20 dB lower than then function tone (the levels vary a bit among systems as dial-up tends to be lower than leased-lines).
At the receiving end you should hear the 2175 and function tone bursts followed by the quieter 2175 -- it's quite noticeable assuming you're listening ahead of?the filter provided in the Tone Remote Adapter. Perhaps the encoder or the decoder has drifted off frequency. 73, Bob, WA9FBO -----Original Message----- From: ve7ltd <[email protected]> To: [email protected] Sent: Mon, 30 Mar 2009 11:22 am Subject: [Repeater-Builder] Motorola Tone-Remote system troubleshooting question All, I am trying to help a local group with a remote TX/RX site they have which is remoted to their office with a leased phone line and some Motorola tone remote equipment. I know the radio end has a Motorola L3276A adapter, and the office end has a "telephone style" handset (don't have the model number). As of last week, this system will no longer transmit. It still receives fine, but will not activate the PTT on the remote radio, or at least there is no transmitted signal. The fact that is receives tells me that at least the line is intact. I have not yet been to the remote site (several miles away) to look at the radio, but I want to know a little more about this tone remote system before I go: 1) Can I plug a regular telephone into the pair to monitor the signaling? 2) How is the signaling done for TX and RX on the 2 wires? 1950Hz tone or something similar? 3) What should I hear on the line when the PTT on the handset is pressed? 4) Is there a way to passively monitor the leased line audio for the signaling from either end with my HP 8920A service monitor? I don't fully understand the concept of balanced lines, and I don't want to damage any of the equipment by connecting something I shouldn't to it. Any help would be appreciated! Dave Cameron - VE7LTD IRLP System Designer
