Unit installation

3-2

or remotes. Sometimes you want this, so you can send tones down the links to control other sites.

Other times, you don't want tones to go down the links; in those cases you should turn on the

DTMF must for the link port transmitters just like you did for your repeater transmitter (with

command 007).

DTMF Mute Bypass:

The DTMF mute bypass can be used for sending DTMF paging codes over a repeater that mutes

DTMF digits or for passing commands out a link transmitter that normally mutes DTMF tones. If

enabled, it allows you press 'D' (or whatever your force-execution digit is - see command 078) as

the first digit after keying up to disable the muting function until you unkey. When the 'D' is

detected, the controller will ignore any digits received from that receiver until you unkey. It will

not mute those digits on any transmitter and it will not try to decode those digits and execute any

commands. The 'D' itself will be muted as soon as it is detected. If you do not have an audio delay

module, the first part of that 'D' will be heard and might mess up whatever you are passing tones to.

If the tones are going to another controller of the same kind, turn off the DTMF bypass on the

other controller so the 'D' won't cause it to ignore the digits. If the first part of the 'D' not being

muted is still a problem, you will have to get an audio delay for that receiver, turn DTMF mute off

and enter the digits without using a 'D' first, or use the controller's command to generate DTMF

digits (command 033).

Voice Falsing

As mentioned earlier, a DTMF decoder works by watching for 8 tone frequencies, 4 that represent

the row and 4 that represent the column of a 16 key DTMF keypad. If a row frequency and a

column frequency are detected at the same time, the decoder registers it as a valid digit.

Sometimes peoples' voices have those frequencies in them and cause the DTMF decoder to think

that a digit is present when it is not. If you have the DTMF mute turned on, this will cause it to be

activated and your voice will "drop out" for a couple of seconds as the controller thinks it is muting

a DTMF digit. If you have the cover tone turned on, you will hear it as well. The voice falsing of

the DTMF decoder is not the decoder's fault - it is just watching for those tones. There are a

couple of things you can do to reduce falsing. The first thing is to check all of your audio levels. If

you have the receive audio turned up too high at any point before it gets to the decoder, it may be

distorted, which adds harmonics and makes falsing more likely. If your audio levels are OK and

you still have falsing problems, you can change a resistor that makes the decoder require that the

row and column frequencies be present longer before it considers the digit to be valid. On the

RLC-3, this resistor is R12 on the radio cards (not the motherboard). When R12 is 300K, the

DTMF digits should be detected in less than 40ms, but voice falsing is common. The first RLC-3's

were shipped this way. Later RLC-3's have used a 470K resistor for R12, which sets the decode

time to about 50ms. This is still a lot faster than most people release digits, so unless you have a

very fast autodialer, it should keep up. This greatly reduces the problems with falsing. In a few

cases, persistent audio distortion problems or someone's voice will cause falsing even with a 470K

resistor. In those cases, that resistor can be replaced with a larger one to slow the decoder down

even more. Values over 700K or so should be avoided as they may keep the decoder from working

at all. You can make any remaining falsing less annoying by setting the DTMF mute timer to be

relatively short (1..2 seconds, or even less if you have an audio delay module).