Icom IC-2GA - Tone Squelch Unit (UT-40); Circuit Description

SECTION 11 UT-40 TONE SOUELCH UNIT
11-1 UT-40 CIRCUIT DESCRIPTION
(1) GENERAL
ІСІ is a tone encoder/decoder which outputs and detects 37
tone frequencies. IC2 functions as a serial/parallel conver-
ter. 6-bit parallel data are applied to IC1. Refer to the
following table for tone frequencies and corresponding
input data.
| OUTPUT ` SEICTINPUT PIN NUMBER | OUTPUT ICT INPUT PIN NUMBER
FREQUE! ei iN FREQUENCY. |-------
ma js[a|sle 7 [8] € з [а [5
T
67.0 HILIHIHIHI|L 136.5 HIHIH|H|L
| AE + +Â
71.9 (рн IH H L 141.3 ЈЕ ЈН ЈН ЕН ЈЕ
F ht - +— --- 1
744 HIHILIH|H|L 146.2 HILIHIHIL
zh T T "> =
77.0 ннн 151.4 нн |
№: 4 жен dee үзген
797 иінін | 156.7 нін THY LI
Јн i 1 +
LIHIHIL
{ +
НЕ
наба +
LiHiL
Бо E
ri! -
|
х т
H|H
| Se Рава И
H H H IH
pe =+
114.8 інн н
31-54 41
118.8 нјнјај(кјнјн
ra —
123.0 (іні | (інін
р 1
127.3 н | нн
нін
11-1
(2) ENCODER
ІСІ (pin 26) outputs the programmed tone frequency when
IC1 (pin 12) becomes "LOW." Q4 functions as a buffer
amplifier. The collector of 04 outputs the tone signal which
is applied to the VCO circuit to be modulated. Tone
deviation is adjusted with R10.
(3) DECODER
The detected tone from the transceiver is applied to IC1
(pin 29). When the signal is tone modulated and the tone
equals the programmed tone frequency, pin 23 becomes
“HIGH.”
When the tone squelch function is turned off, IC2 (pins 11
and 12) are “HIGH.” +5 V are not applied to IC1. Q2 and Q3
are turned off and the TSQL line is “HIGH.”
When the tone squelch function is turned on, ІС2 (ріп 11) is
"HIGH" and ІС12 (ріп 12) is "LOW." Q2 апа ОЗ are turned
on.
When the received tone frequency equals the programmed
tone frequency, pin 23 is "HIGH" and the TSQL line is
"HIGH."
When the received tone frequency does not equal the
programmed tone frequency, IC1 (pin 23) is "LOW," and
the TSQL line is "LOW."