To send DTMF digits quickly (40/40) you need to be using an automated encoder since you could not press each button by hand that fast. An automated encoder is also called a “Store and Forward” encoder. You “Store” the DTMF code into the device when you program it, then “Forward” it to send the entire DTMF code as one complete DTMF string of numbers and characters.
Store and forward encoders can be a programmable microphone or two-way radio, a stand-alone encoder such as the ENC-3300, or part of a large law enforcement dispatch console. In the end they all perform the same function of sending out DTMF digits and characters.
If you are sending each DTMF digit by pressing each button individually, then you are sending the code “Manually”.
If the operator entering the codes manually delays too long between sending each DTMF digit, the decoder may time-out and not accept the code. Many decoders time-out after one second, so the operator must enter each digit promptly and without delay. Genave decoders are adjusted via software and can have their timing changed in 10’th of a second steps from .1 second to 25 seconds. When ordering, if you indicate you are only using an Automatic encoder, the decoder is set to 600 msec. If you specify you will be sending the DTMF code manually, or both Automatic and/or Manually, the decode rate is set to 3 seconds which should allow enough time for an operator to send the code. The entire code does not need to be sent within three seconds, but the operator must press at least one key every three seconds to keep the RXC decoder active and waiting to clock-in the entire code.
Encoders from different manufacturers have various speeds as their standard. As mentioned before, Whelen uses 40/20 or faster, Federal Signal uses 40/40 or slower, while Motorola Law Enforcement Consoles use the amazingly slow 250/250 msec. This is Motorola’s standard even on the latest Centracom Elite, touch screen consoles. If you are in charge of ordering a new Mot console, you should consider ordering it with a “Special” encoder option (called an “SP”) which would increase the DTMF speed to 40 msec /40 msec. Motorola’s standard 250/250 speed is just a waste of air-time.
Please don’t let the DTMF Mark/Space timing or the details about Manual vs Automatic throw you or keep you from using DTMF codes. We really like DTMF codes. They offer much more flexibility than standard two-tone paging signals. If you or your radio service people have any questions about DTMF codes, timing, etc., please feel free to give Genave a call and discuss it with our engineers.