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2241A Distribution Panel

GENERAL

Section 1

1 - 2

1-6 PTT BUFFERING

. High current PTT Outputs

permit direct drive of transmitters requiring up to 100
mA keying current. The Panel accepts 12 or 24 low
current PTT Inputs and provides high current outputs.
Two switches permit the PTT Circuits to be configured
for Distribution or Buffering (Distribution

OFF

). The first

switch controls PTT Outputs 1-12, the second controls
PTT Outputs 13 -24. This arrangement permits a
combination of both Distributed and Buffered PTT
Circuits. That is, 12 Outputs can be set for Distribution
and 12 PTT Circuits can be set to Buffer

Mode. In either

mode, the front panel PTT Controls are operational.

1-7 PTT CONVERSION

. Each PTT Circuit has two

independent PTT Logic Switches which select among:
E/M, TTL, and Digitac Logic types. One switch (INPUT)
configures the PTT Detector, and the other configures
the PTT Output. PTT Logic conversion is simply a
matter of selecting the desired Input and Output Logic
Types.

1-8 KEY DETECT

. Two switches permit each Key

Detector to be set to accept a wide variety of PTT Logic
Types. The

INPUT LOGIC

Switch selects among: E/M,

TTL, and Digitac Logic types. The

E/M SELECTOR

provides a choice of E/M Type, or it

is used to invert

TTL or Digitac PTT Logic

- when needed.

INPUT LOGIC

Switch.

This three position switch

selects among: E/M, TTL, and Digitac Logic types by
setting the detector trip voltage and the voltage on the
pull-up resistor. The purpose of the pull-up resistor is to
force an idle condition if the PTT Input circuit is open or
not asserted.

E/M SELECTOR Switch.

This two position switch

selects the E/M Type or an INVERT function.

Position 1

is used for

Type: I, II, or III M Lead

Inputs. In this

position the “pull-up” resistor is connected to the
detector ground and PTT is asserted when the Input is
less than ( more negative ) -20 Volts.

Position 2

is used

for

E Leads

Type IV or V M Lead

Inputs. In this

position the “pull-up” resistor is connected to

“SB”

Signal Battery / -48 Volt Input Lead and PTT is asserted
when the Input is greater than ( more positive ) -20
Volts.

Position 2

is also used to

INVERT TTL or

Digitac

Logic when needed.

In this case

, PTT is

asserted when INPUT Lead is open or high.

1-9 PTT DISTRIBUTION.

The 2241A can be set so that

individual PTT Inputs can be distributed to multiple PTT
Outputs. Two DISTRIBUTION switches control this
function. The first switch controls PTT Outputs 1-12, and
the second switch controls PTT Outputs 13-24. When
the

DISTRIBUTION Switch is ON

, multiple PTT

Outputs will track the state of an individual PTT Input. In
this case, the PTT distribution fan-out tracks the audio
distribution fan-out which is determined by the state of
seven, Audio Distribution Switches. For example, if
Audio Input 1 is set for distribution to Audio Outputs 1-6,
then PTT Input 1 will be distributed to PTT Outputs 1-6.
When the

DISTRIBUTION Switch is OFF

, each PTT

Outputs will track the state of its individual PTT Input.

1-10 PTT OUTPUT Circuit

. Each PTT Output circuit

provides a contact closure when PTT is asserted
(transmitter keyed). There is an independent, three
position,

PTT Logic Switch

for each PTT Output

Circuit. This switch which selects among: E/M, TTL, and
Digitac Logic types and selects the voltage for the pull-
up resistor.

PTT OVERRIDE Switch

. Each PTT Output Circuit has

a PTT Override Switch located on the front panel of the
2241A. The PTT Override Switch permits manual
control of PTT to facilitate installation, trouble shooting,
or temporary reconfiguration of a radio system. This is a
three position, lighted, toggle switch with the center
position being the

NORMAL

setting. In the Normal

Position, the PTT Output tracks the PTT Input and the
switch bat lights up

GREEN

when PTT is asserted. In

the

KEY

(UP)

Position, the switch bat lights up

RED

and

the PTT Output is asserted, regardless of the state of
the PTT Input. In the

DISABLE

(DOWN) Position, the

switch bat lights up

RED

and the PTT Output is

disabled, regardless of the state of the PTT Input.

1-11 AUDIO INPUT Circuits

. Eight Audio Input Circuits

are provided. These circuits are balanced and floating
with a fixed 600 Ohm Input Impedance. They can be
driven from a balanced or single ended source.

1-12 AUDIO INPUT / SUM Circuits

. Eight Audio Input

Sum Circuits are provided. These circuits are primarily
used to sum (voted) receiver audio with transmit audio.
They are balanced and floating and have an

Input

Impedance Switch.

This switch is set to

HI Z

( 20 K

Ohms) when the sum input is paralleled with (bridging)
another 600 Ohm Input. It is set to

600

Ohms when the

sum input is used to terminate a circuit,

or when the

Sum Input is not in use.

1-13 AUDIO OUTPUT Circuits

. There are 24 Audio

Output Circuits. These circuits are balanced and floating
with a fixed 600 Ohm Output Impedance. They can be
terminated with a balanced or single ended load. The
(Input to Output) gain of the audio circuits is factory set
to unity / 0.0 dB. However, a

front panel

, screw

adjustment,

GAIN CONTROL

is provided for

normalizing transmitter deviation. This control has a
range of

+/- 10 dB

(0.316 to 3.16) with a logarithmic

characteristic that provides a constant dB gain change
per degree of rotation. Use of 15 turn potentiometers
provides high resolution control.

* Digitac is a Trademark of Motorola Inc.

M:IV,V,E

M:I,II,III