Lathem GPS Receiver DDC2 RS User Manual
LTR-GPS Satellite Synchronizer  
Installation &  
Setup Guide  
 
Contents  
Welcome ..............................................................................................................1  
Package Contents  
Specifications  
Configure Settings..............................................................................................3  
Time Zone  
Daylight Savings  
ASCII Output (optional)  
Install the Antenna..............................................................................................5  
Connect Slave Devices.....................................................................................10  
LTRx-512 Master Clocks  
LTR0 and DWA-S (Sonachron)  
DDC Series Digital Wall Clocks  
Warranty ............................................................................................................12  
 
LTR-GPS Installation and Setup Guide  
CHAPTER 1  
Welcome  
Lathem’s LTR-GPS is a Global Positioning Satellite receiver using 12-channels to  
access the accurate date and time signal transmitted each second by 24 satellites in  
geosynchronous orbit around the globe.  
The package includes an amplified GPS Antenna, which must be mounted out-doors  
or beneath a roof sky-light, facing skyward. An integrated cable links the Antenna to  
the LTR-GPS Receiver Module, which should be mounted in-doors.  
The Receiver Module verifies and reformats the received satellite data, and offers  
multiple synchronization protocol outputs:  
The RS-485 Output can directly synchronize up to 31 Lathem time products, up to  
4000ft away, over a single twisted-pair from a user-provided Cat-3 or Cat-5 cable.  
The length of cable and number of synchronized devices can be further increased  
using Lathem’s “SWIFT485+” RS-485 Converter / Repeater.  
An included RS-232 interface provides a periodic “Time Stamp” transmission,  
“MM-DD-YYYY HH:MM:SS cr”, for use by computing systems having custom  
software to incorporate accurate date and time records in their applications: 9600,  
N, 8, 1. Use of this option requires Lathem cable, Part No. SAE0370, to be  
ordered separately.  
Simple DIP-Switch set-up enables the installer to specify Local Time Zone, Daylight  
Savings Time corrections, and output formats. An LED indicator shows Signal  
Reception / Protocol Mode.  
The LTR-GPS may receive its power from an LTRx-512-series Master Clock, using  
2nd cable pair, if the distance is less than 200ft; else, power is provided locally by a  
9vAC Power Adapter.  
.
Page 1  
 
 
LTR-GPS Installation and Setup Guide  
The LTR-GPS package includes the following:  
• LTR-GPS Satellite Synchronizer  
• 115vAC, 2.7w, 50/60Hz Power Adapter  
• Active GPS Antenna with 25ft. Cable  
• Antenna Mounting Bracket and Hardware  
LTR-GPS Specifications:  
• Size / Weight  
3.25”x 2”x6.6” / 1 lb.  
• Power:  
6-12vAC/DC, 300mA (max)  
FCC Part-15, ICES003  
•
Certificates:  
Model numbers of the devices supported by LTR-GPS:  
LTR-0  
Master Clock  
DWA-S  
Sonochron  
LTR4-512  
LTR8-512  
LTR8-512M  
DDC2-RS  
DDC2-RS-24  
DDC4-RS  
DDC4-RS-24  
Master Clock  
Master Clock  
Master Clock w/ Modem  
2” Digital Wall Clock 115v  
2” Digital Wall Clock 24v  
4” Digital Wall Clock 115v  
4” Digital Wall Clock 24v  
Page 2  
 
LTR-GPS Installation and Setup Guide  
C H A P T E R 2  
Configure Settings  
1. Remove the two Philips-head screws on each end of the unit. Gently flex apart  
and lift the cover to expose the circuit board inside.  
2. Locate the 8-position DIP switch and hold the unit on a table so that the  
switch numbers can be viewed in the following order:  
SWITCH  
SWITCH  
SWITCH  
SWITCH  
SWITCH  
SWITCH  
SWITCH  
SWITCH  
1
2
3
4
5
6
7
8
Adjust  
Plain Text  
Output for  
Time Zone,  
DST  
Standard /  
Custom  
Protocols  
Enable  
DST (U.S.)  
Time Zone  
3. Set Time Zone switches 4-8 for the code representing the offset from GMT  
(Greenwich Mean Time) of your location. For installations in the U.S.,  
Canada and Mexico, the codes are as follows:  
SWITCH SWITCH SWITCH SWITCH SWITCH  
Time Zone Country Offset  
4
5
6
7
8
Greenwich Mean  
Time  
0 Hrs.  
-4 Hrs.  
-5 Hrs.  
-6 Hrs.  
-7 Hrs.  
-8 Hrs.  
-9 Hrs.  
-10 Hrs.  
Closed  
Closed  
Closed  
OPEN  
OPEN  
Atlantic Time  
Eastern Time  
Central Time  
Mountain Time  
Pacific Time  
Alaska  
CAN  
Closed  
Closed  
Closed  
Closed  
Closed  
Closed  
Closed  
Closed  
OPEN  
OPEN  
OPEN  
OPEN  
Closed  
Closed  
Closed  
OPEN  
OPEN  
Closed  
Closed  
OPEN  
OPEN  
Closed  
OPEN  
Closed  
OPEN  
Closed  
OPEN  
Closed  
OPEN  
Closed  
Closed  
Closed  
Closed  
Closed  
Closed  
US, CAN,  
MEX  
US, CAN,  
MEX  
US, CAN,  
MEX  
US, CAN,  
MEX  
US  
US  
Hawaii  
Page 3  
 
 
LTR-GPS Installation and Setup Guide  
4. Set Daylight Savings Time switch 3 according to the following table to enable  
U.S. rules: 2:00AM first Sunday in April and last Sunday in October:  
SWITCH  
Daylight  
Savings  
3
Enable  
OPEN  
Disable  
Closed  
5. Switch 2 is used for custom ordered protocols only. This should normally  
be left in the OPEN position.  
6. If using the RS232 port (requires cable # SAE0370, sold separately) to  
transmit a plain text “time stamp”, OPEN switch 1 to select Local Time  
transmission. Close switch 8 to transmit GMT.  
SWITCH  
RS-232  
Time Stamp  
1
Local Time  
OPEN  
G.M.T.  
Closed  
Format for ASCII output: “MM-DD-YYYY HH:MM:SS cr”.  
Communications Port Settings: 9600, N, 8, 1  
7. Re-align and gently flex apart the cover to replace it over the chassis, making  
sure that the circuit board connectors protrude through the appropriate side  
cut-outs. Secure the cover with the four (4) screws previously removed.  
Page 4  
 
LTR-GPS Installation and Setup Guide  
C H A P T E R 3  
Install the Antenna  
The antenna must be installed in a position that will have line of sight with three  
satellites.  
Page 5  
 
 
LTR-GPS Installation and Setup Guide  
After setting the LTR-GPS switches, then mount the active antenna. Locate  
the antenna at the highest elevation possible, with a wide view of  
unobstructed, open sky. If possible, avoid mounting the antenna on the north  
side of a building, which might block exposure to satellites.  
Proper locations for antenna mounting:  
Page 6  
 
LTR-GPS Installation and Setup Guide  
Avoid these locations when mounting antenna:  
1. Using two (2) supplied screws, attach the satellite antenna to the mounting  
bracket. Do not over-tighten the screws.  
Page 7  
 
LTR-GPS Installation and Setup Guide  
2. If you have Lathem’s Installation Kit (P/N GPS-INSTALL-TOOLS sold  
separately), then connect the 9v battery plug to the LTR-GPS’ power jack and  
the piezo beeper to the exposed shunt pins: Red to (+) and Black to (-).  
Connect the antenna cable to the LTR-GPS Module. Hold the antenna in its  
intended mounting position. If the antenna has exposure to the GPS satellites,  
within three (3) minutes the LED will flicker and the beeper will ‘chirp’ once  
per second. Afterwards, the LED should start flashing once per minute, and  
the beeper will ‘beep’ for 1-second. These signals confirm proper antenna  
placement and system functionality, prior to anchoring the antenna bracket.  
3. One method is to attach the bracket-mounted antenna to the outside of your  
building or on the roof’s parapet with antenna facing skyward and unblocked  
by architectural impediments. An alternate method is to mount the antenna  
indoors, beneath a “skylight” window. Do not mount the antenna directly on  
the roof surface where it might get submerged by storm water. Its enclosure is  
rain-proof when properly installed, but is not designed for submersion.  
4. Insert supplied nylon tie-wrap through raised loop of the plastic clamp at the  
end of the unit (Fig. 1). Do NOT close the tie-wrap yet. If plastic cable  
clamps are not already secured to the LTR-GPS unit, then attach where shown  
in Fig.1 by peeling off protective paper backing and adhering to the metal  
surface with firm pressure. Allow the adhesive to set for 5 minutes before  
securing the cables.  
GPS RECEIVER / SYNCHRONIZER  
LATHEM TIME CORP.  
200 SELIG DRIVE SW, ATLANTA, GA 30336 USA  
(800) 241-4990  
LTR-GPS  
Fig. 1 - LTR-GPS Unit  
Page 8  
 
LTR-GPS Installation and Setup Guide  
5. Mount the LTR-GPS unit to an indoor surface within the 25 foot antenna  
cable length using four (4) screws and anchors if needed (not supplied). Do  
not attempt to extend this Cable.  
6. Plug the antenna cable into the antenna jack on the LTR-GPS unit and secure  
the cable in the plastic clamp for strain relief (Fig.1).  
7. If the LTR-GPS will not be powered by an LTRx-512 Master Clock, then  
insert the plug from the wall wart power adapter into its mating jack. Plug the  
power adapter into a nearby AC outlet. Verify that the red LED indicator  
flashes “on” during initial power-up.  
8. Observe the LED indicator on the LTR-GPS unit for 3 minutes until a satellite  
signal is received, upon which the light should start blinking each second. A  
brighter flash should occur approximately every 16-seconds. The LED not  
flashing as described above indicates that the antenna is disconnected, that the  
antenna is improperly positioned, or that power is not supplied to the unit.  
Page 9  
 
LTR-GPS Installation and Setup Guide  
C H A P T E R 4  
Connect Slave Devices  
1. Connect a category 3 or 5 cable to the terminal block using a small, flat-blade  
screwdriver. Connect one of the four twisted-pairs of the cable to the D+/D-  
terminals on the LTR-GPS unit. This provides synchronization commands to the  
Lathem slave devices. Connect the other end of the selected pair to the SYNC_IN  
D+/D- terminals of a Lathem LTRx-512-series master control (Fig.2) or to  
Lathem DDCx Series digital wall clocks (Fig.4). Be sure to maintain consistent  
polarity of the D+/D- signals. If the LTR-GPS will be powered by a Lathem  
master control within a 200 foot proximity, then connect another twisted-pair to  
the terminals marked ‘~’ on both devices (Fig.2).  
2. Secure the power and data cables to the LTR-GPS unit using the tie-wraps  
(Fig.1). Connect the data cable(s) to Lathem slave time display devices to be  
controlled. The twisted-pair data cable can supply data for 31 (max) devices  
located within 4,000 feet. Simply daisy-chain the twisted-pair from slave to  
slave, maintaining consistent polarity for the D+ / D- signals. A Lathem  
SWIFT485+ RS-485 Bus Repeater allows for more than 31 devices or cable  
lengths beyond 4,000 feet.  
3. Connect the Lathem slave devices using the twisted pair from the RS485 cable  
according to the User Manual instructions for each device.  
4. If the LTR-GPS will be connected to an LTRx-512 master control that is already  
in operation, then the master will not immediately recognize the signal from the  
LTR-GPS. It will start recognizing the GPS signal within 15 minutes past  
midnight or after power-up. To accelerate the recognition process, the installer  
may power-off / power-on the Master by carefully removing the front panel and  
toggling the internal power switch, or by briefly disconnecting the Master from its  
AC power source. BE CAREFUL: HAZARDOUS VOLTAGES ARE PRESENT.  
Page 10  
 
 
LTR-GPS Installation and Setup Guide  
Fig.2 - Connect to LTRx-512 Master Clock  
4000 FT. MAX  
200 FT. MAX;  
ELSE USE POWER ADAPTER  
Fig.3- Connect to LTR-0 or DWA-S (Sonachron)  
YELLOW  
WHITE  
YELLOW  
WHITE  
LTR-0  
DWA-S  
Fig.4 - Connect to DDC Series Digital Wall Clock  
DDC2-RS / DDC4-RS  
Page 11  
 
LTR-GPS Installation and Setup Guide  
Warranty  
Limited One-Year Limited Warranty  
Lathem warrants the hardware products described in this guide against defects in material and workmanship for a  
period of one year from date of original purchase from Lathem or from an authorized Lathem reseller. The conditions  
of this warranty and the extent of the responsibility of Lathem Time Corporation (“Lathem”) under this warranty are  
listed below.  
1. This warranty will become void when service performed by anyone other than an approved Lathem warranty  
service dealer results in damage to the product.  
2. This warranty does not apply to any product which has been subject to abuse, neglect, or accident, or which has  
had the serial number altered or removed, or which has been connected, installed, adjusted, or repaired other  
than in accordance with instructions furnished by Lathem.  
3. This warranty does not cover dealer labor cost for removing and reinstalling the machine for repair, or any  
expendable parts that are readily replaced due to normal use.  
4. The sole responsibility of Lathem under this warranty shall be limited to repair of this product, or replacement  
thereof, at the sole discretion of Lathem.  
5. If it becomes necessary to send the product or any defective part to Lathem or any authorized service dealer,  
the product must be shipped in its original carton or equivalent, fully insured with shipping charges prepaid.  
Lathem will not assume any responsibility for any loss or damage incurred in shipping.  
6. WARRANTY DISCLAIMER AND LIMITATION OF LIABILITY: Except only the limited express warranty  
set forth above, the products are sold with no expressed or implied warranties of any kind, and the implied  
warranties of merchantability and fitness for a particular purpose are hereby expressly disclaimed. No  
warranties are given with respect to products purchased other than from Lathem or an authorized Lathem  
reseller and any such products are purchased "as is, with all faults." In no event will Lathem be liable for any  
direct, indirect, special, incidental or consequential damages arising out of or in connection with the delivery,  
use or inability to use, or performance of this product. In the event any limited remedy given herein shall be  
deemed to have failed of its essential purpose, Lathem's maximum liability shall be to refund the purchase price  
upon return of the product.  
7. Proof of date of purchase from Lathem or an authorized Lathem reseller is required for warranty service on this  
product.  
8. This Warranty grants specific legal rights. Additional legal rights, which may vary by locale, may also apply.  
9. Should any difficulties arise with the performance of this product during warranty, or with any Lathem  
authorized service centers, contact Lathem Time at the address below.  
Lathem Time  
200 Selig Drive, SW, Atlanta, GA 30336  
404-691-0405  
www.lathem.com  
Page 12  
 
 
Document # USG0045A  
 

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