Codan Radio P25 Training Guide - Manual (Page 54)

TRAINING GUIDE | P25 RADIO SYSTEMS
Chapter 3: P25 Technical Information Page 46
P25 VS. ANALOG DELAY TIMES
Delay times between legacy analog equipment and P25 digital equipment may vary.
In order to understand the different delay times, the following defi nitions for an analog system are as
follows (from TIA-603-C):
Receiver Attack Time
Receiver attack time is the time required to produce audio power output after application of a modulated
input signal.
Carrier Attack Time
Transmitter carrier attack time is the time required to produce 50% of steady-state carrier output power
after changing the state of the transmitter from standby to transmit.
If an analog system uses CCTSS decode and / or encode the following defi nitions are applicable (from
TIA-603-C):
Receiver Audio Attack Time (CTCSS)
The receiver audio attack time is the elapsed time between the application of a receiver input signal
12 dB above the reference sensitivity modulated with the standard test modulation and standard
subaudible modulation, and the time that the audio voltage at the receiver output is greater than 90%
of its rated output.
Encoder Response Time (CTCSS)
The encoder response time is the elapsed time from the moment the push-to-talk control circuit is
activated at the transmitter until the CTCSS tone at the output of the transmitter has reached 90% of
maximum voltage.
According to TIA-603-C an analog system could have a maximum Receiver Attack Time of 150 ms (250
ms if CTCSS is used) and a maximum Transmitter Attack Time of 100 ms (150 ms if CTCSS is used). In
most analog systems the attack times are signifi cantly lower than these values (especially if the system
does not have CTCSS).