When the first SINCGARS radio (the RT-1439, and later the RT-1523) came out is was a real PITA (Pain In The A..) to get it all keyed up for use.  The following would need to be done:

1. Using the MX-18290 (or other hop set loader) the hop set needs to be loaded.  There are two parts to doing this:
1. The allowable frequencies to be used are specified (maybe 250 bytes + parity and check sum bits)
2. There may be a frequency lockout set loaded, but this is optional.
   
3. The order in which the frequencies are used is specified is the Transmission Security Key (TSK) (different from a TEK)
   
2. Using one of the common crypto loaders, like the KOI-18, the Voice encryption Keys (TEK) would be loaded into a separate KY-57 Transmission Security Device.  On the newer RT-1539 SINCGARS the KY-57 is built in, but still needs it's keys loaded.
   
3. Using one of the common crypto loaders, like the KOI-18, the GPS key is loaded into a or PSN-10 SLGR or PSN-11 PLGR  GPS receiver and with a time fill cable the date and time are loaded into the SINCGARS radio to sync the hop set.  The GPS really does not need to be keyed to get the correct time, except in a case where someone is spoofing the GPS system, which probably has not yet happened.  This may only need to be done on the Net Control Operator's radio, not sure.
   

You can see this is a lot of work and requires many different devices.  One simplification  is to use the more modern key fill devices like the Crazy-10 and another is to use a laptop computer with a special cable on the serial port.  The latter is what this cable does.

The Government sealed bag is marked:
7050-01-355-9729
CAGE 65242 P/N A3157830
CONVERTER
1 ea  A  05/97
RE/MARK   DLA/RT

The cable label is:
80063-A3157830
PC/FILL-SINCGARS
(4FT 0IN) 04/94
MFR 65242

On the cable itself in white paint:
4Q94 USE BY 4Q02

The later marking appears to be saying the cable was made in the forth quarter of 1992 and has an expiration date of the fourth quarter of 2002.
Why the 10 year life?

On the back of the printed circuit board in the pipe the serial number "4" is hand marked.

Using a Fulke 87DMM to make some basic measurements:

DB-9(f)	PC Function	Wire Color	U-183 6 pin Audio
1 = 4	DCD	Brn
2	Rx	n.c.
3	Tx	Org
4 =1	DTR	Yel
5	Gnd	Blk	A = C
6	DSR	n.c.
7	RTS	n.c.
8	CTS	Red
9	RI	n.c.

The meaning of the PC lines is based on the connection to a phone line modem.  They are:
DCD = Data Carrier Detect
Rx = the data comint into the PC
Tx = the data leaving the PC
DTR = Data Terminal Ready
Ground
DSR = Data Set Ready
RTS = Request To Send
CTS = Clear To Send
RI = Ring Indicator

SINCGARS FILL connector pinouts:
A = Ground
C = Fill Request
D = Fill Data in
E = Fill Clock in
B, F - no connection

The cable has a 1 inch diameter x 3.5" long cylinder "pipe" in line.  From the above readings it appears to contain active circuitry, not just filtering.
Using the Fluke 87 in Diode mode

Red/Black -> |              V	A	B	C	D	E	F
A	0	-	0	-	2.132	-
B	-	0	-	-	-	-
C	0	-	0	-	2.132	0
D	.716	-	.716	0	2.586	-
E	.709	-	.709	-	0	-
F	-	-	-	-	-	0

Where - means Over Loading the meter or open circuit.

Pins A, C, D and E are connected to semiconductors.
Maybe pins B and F are connected to high impedance inputs.

This cable does NOT use Tx data from the computer in the conventional way.  The Tx data pin is just a DC power supply, not any kind of data.
Inside the CV-4228 "pipe" are a couple of opto isolators, used as logic elements rather than for isolation.  Clock and data are feed using bit banging of the COM port handshake lines. 

For key loading:

• Fill Clock (pin E) is RTS on the serial port
• Fill Data (pin D) is DTR on the serial port
• Start with Fill Data (DTR) High (Fill Clock, RTS does not matter)

CTS will start off high, but when a fill request (PTT pressed on receiving device) CTS will go low to signal the fill request.
It stays low during the fill.
After a successful fill it probably will go back high.

To simulate the sprocket (small) holes in a paper tape:

• set DTR for the desired data bit
• make RTS high
• wait a little
• make RTS low
• wait a little
• setup next data bit.

9 May 2004 - if the KY-57 makes a fill request and data is loaded into the KY-57 that does not validate then CTS remains low, i.e. the fill request does not stop.  The KY-57 needs to be powered down to turn off the fill request.

July 2005 - Have written a number of LabView programs to interface with the CV4228.

TM 11-7010-263-13&P-1 Vol 1 of 3
Operator's, Unit, and Direct Support Maintenance Manual (Including Repair Parts andd Special Tools List) for:
Computer System, Digital (AN/GYQ-73) (Automated Comsec Management and Engineering System (ACMES) - Phase I) Operator's, Unit, and Direct Support Maintenance Manual (Including Repair Parts and Special Tools List) for:
V2 Computer, Digital Lightweight Computer (Model CP-2112(V)2/U) (NSN 7021-01-347-8742) (EIC: N/A)
V2 Lightweight Printer (Model PT-555/U) (7025-01-347-8720) (EIC: N/A)
Random Data Generator AN/CSZ-9 (5820-01-349-9309) (EIC: N/A)
Automated Net Control Device AN/CYZ-10 (5810-01-343-1194) (EIC: N/A)
Converter, Digital-to-Digital Cable CV-4228/U (7050-01-355-9729) (EIC: N/A) Including Revised BECS (RBECS) Application Software and RBECS Data Transfer Device Application Software (RDS) (this item is icluded on EM 0164)

TM 11-7010-263-13&P-2 Vol 2 of 3
Operator's, Unit, and Direct Suport Maintenance Manual (Including Repair Parts andd Special Tools List) for:
Computer System, Digital AN/GYQ-73 (Automated COMSEC Management and Engineering System (ACMES) - Phase I)
V2 Computer, Digital/ Lightweight Computer CP-2112(V)2/U (NSN 7021-01-347-8742) (EIC: N/A)
V2 Lightweight Printer PT-555/U (7025-01-347-8720) (EIC: N/A)
Random Data Generator AN/CSZ-9 (5810-01-349-9309) (EIC: N/A)
Automated Net Control Device AN/CYZ-10 (5810-01-343-1194) (EIC: N/A)
Converter, Digital-to-Digital Cable CV-4228/U (7050-01-355-9729) (EIC: N/A) Including Revised BECS (RBECS) Application Software and RBECS Data Transfer Device Application Software (RDS) (this item is icluded on EM 0164)

TM 11-7010-263-13&P-3  Vol 3 of 3
Operator's, Unit, and Direct Suport Maintenance Manual (Including Repair Parts andd Special Tools List) for:
Computer System, Digital AN/GYQ-73 (Automated COMSEC Management and Engineering System (ACMES) - Phase I)
V2 Computer, Digital/ Lightweight Computer CP-2112(V)2/U (NSN 7021-01-347-8742) (EIC: N/A)
V2 Lightweight Printer PT-555/U (7025-01-347-8720) (EIC: N/A)
Random Data Generator AN/CSZ-9 (5810-01-349-9309) (EIC: N/A)
Automated Net Control Device AN/CYZ-10 (5810-01-343-1194) (EIC: N/A)
Converter, Digital-to-Digital Cable CV-4228/U (7050-01-355-9729) (EIC: N/A) Including Revised BECS (RBECS) Application Software and RBECS Data Transfer Device Application Software (RDS) (this item is icluded on EM 0164)