Theory of Operation
11
MT-3 FM Transmitter Mainboard Instruction Manual
IM20-MT3TXMN
time-out-timer Circuitry
The MT-3 FM Transmitter also has an
associated programmable push-to-talk
(PTT) time-out-timer (TOT) circuitry on the
transmitter mainboard. The TOT circuitry
is powered via J34 from the continuous
+9.5 VDC supply and is programmable for
various time-out periods.
The TOT input trigger (enabled by J33) is
normally high and in this state the timer is
disabled. When the input trigger level falls
below +2.0 VDC, the timer is activated, the
TOT output trigger (enabled by J35) is pulled
low and the transmitter is keyed. If the input
trigger rises above +2.4 VDC or if the time-
out period is exceeded, the output trigger will
go high, disabling the transmitter. If the time-
out period is exceeded, the TOT input trigger
must go high and then low again in order to
re-key the transmitter.
The time-out duration is jumper selectable
from 1 second to 8 hours (see Table 1).
The positions of the jumpers are on the
top (through-hole component) side of the
transmitter mainboard.
J32 J31 J29 J28 J26 J27
Minutes
I
I
I
I
I
I
0.01
I
I
I
I
I
n/I
0.01
I
I
I
I
n/I
I
0.01
I
I
I
n/I
I
I
0.01
I
I
I
n/I
I
n/I
0.02
I
I
n/I
I
I
I
0.02
I
I
I
n/I
n/I
I
0.03
I
I
n/I
I
I
n/I
0.04
I
I
n/I
n/I
I
I
0.05
I
I
n/I
I
n/I
I
0.06
I
I
n/I
n/I
I
n/I
0.08
I
n/I
I
I
I
I
0.10
I
I
n/I
n/I
n/I
I
0.12
I
n/I
I
I
I
n/I
0.15
I
n/I
I
n/I
I
I
0.19
I
n/I
I
I
n/I
I
0.23
I
n/I
I
n/I
I
n/I
0.31
I
n/I
n/I
I
I
I
0.38
I
n/I
I
n/I
n/I
I
0.47
I
n/I
n/I
I
I
n/I
0.62
I
n/I
n/I
n/I
I
I
0.75
I
n/I
n/I
I
n/I
I
0.94
I
n/I
n/I
n/I
I
n/I
1.25
n/I
I
I
I
I
I
1.5
I
n/I
n/I
n/I
n/I
I
1.88
n/I
I
I
I
I
n/I
2.5
n/I
I
I
n/I
I
I
3.0
n/I
I
I
I
n/I
I
3.75
N/I
I
I
N/I
I
N/I
5.0
n/I
I
n/I
I
I
I
6.0
n/I
I
I
n/I
n/I
I
7.5
n/I
I
n/I
I
I
n/I
10
n/I
I
n/I
n/I
I
I
12
n/I
I
n/I
I
n/I
I
15
n/I
I
n/I
n/I
I
n/I
20
n/I
n/I
I
I
I
I
24
n/I
I
n/I
n/I
n/I
I
30
n/I
n/I
I
I
I
n/I
40
n/I
n/I
I
n/I
I
I
48
n/I
n/I
I
I
n/I
I
60
n/I
n/I
I
n/I
I
n/I
80
n/I
n/I
n/I
I
I
I
96
n/I
n/I
I
n/I
n/I
I
120
n/I
n/I
n/I
I
I
n/I
160
n/I
n/I
n/I
n/I
I
I
192
n/I
n/I
n/I
I
n/I
I
240
n/I
n/I
n/I
n/I
I
n/I
320
n/I
n/I
n/I
n/I
n/I
I
480
N/I = Not Installed
I = Installed
Bold
text represents default settings.
TABLE 1: Time-out Jumper Settings and Duration
Содержание MT-3 Series
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