TELEPHONE LINE ANALYZER KIT MODEL TT-400K Assembly and Instruction Manual Elenco Electronics, Inc. Copyright © 1994 Elenco Electronics, Inc.
INTRODUCTION Are you planning to install a new telephone? Are you having a problem with a newly installed telephone? Then the Model TT-400 Telephone Line Analyzer Kit will help you pinpoint exactly where the problem is. The TT-400 connects between your telephone and the telephone wall jack and performs the following four tests: a) Line Test - Verifies the DC voltage to your telephone. b) Ring Test - Verifies the AC ranging voltage to your telephone.
TELEPHONE OPERATION The primary purpose of the telephone is to transmit and receive voice signals allowing two people with telephones to communicate with each other. To be of practical value, the telephone must be connected to a switching network capable of connecting each telephone to many other telephones. To accomplish this switching, each subscriber telephone is connected to the telephone company’s Central Office by two wires referred to as the local loop.
fixed rate. This switch is in series with the hook switch. Opening the switch interrupts the current in the local loop. A series of current pulses is thus sent out on the local loop as shown in Figure 3. The number of pulses sent corresponds to the digit dialed. Dialing a 0 sends ten pulses. The dial pulses are sent at a rate of 10 pulses per second (100mS between pulses). Each pulse consists of a mark interval (loop current).
RINGER Bell Hammer As shown in Figure 2, the ringer is connected across the tip and ring inputs in series with a capacitor to block the 48VDC. The ringer consists of a permanent magnet attached to an armature as shown in Figure 7. When an alternating current of 20Hz is passed through the coils, the armature is alternately attracted to one coil and then the other. The hammer attached to the armature thus strikes one bell and then the other to produce the ringing sound.
CONSTRUCTION Introduction The most important factor in assembling your Telephone Line Analyzer is good soldering techniques. Using the proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is recommended. The tip of the iron must be kept clean at all times and well tinned. Safety Procedures • Wear eye protection when soldering. • Locate soldering iron in an area where you do not have to go around it or reach over it. • Do not hold solder in your mouth.
ASSEMBLY INSTRUCTIONS INTRODUCTION Assembly of your TT-400K Telephone Line Analyzer will prove to be an exciting project and give much satisfaction and personal achievement. If you have experience in soldering and wiring technique you should have no problem in the assembly of this kit. Care must be given to identifying the proper components and in good soldering habits. Above all, take your time and follow the easy step-by-step instructions. Remember, “An ounce of prevention is worth a pound of cure”.
ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD In all of the following assembly steps, the components must be installed on the top legend side of the PC board. The board is turned to solder the component leads on the foil side.
Mount the Meter Take off the four nuts, lockwashers and washers from the mounting screws on the meter. Insert the meter into the case from the front. Replace the four washers, lockwashers and nuts onto the meter as shown in Figure D. Meter Figure D Washer Lockwasher Nut Telephone Cable Assembly Feed about 5” of telephone cable through the front panel as shown. If the loose end of the telephone cable is not already stripped, strip off 1 1/2” of outer casing to expose the four wires.
J4 Modular Jack J3 Green Cut off the yellow and black wires at the base of the modular jack (they are not used). Cut the red and green wires to 4” and strip 1/4” of insulation off of each wire. The spade lugs (if any) are not used. Jack Red Insert the red wire into hole J3 from the foil side of the PC board as shown in Figure G. Solder wire into place. Figure G Follow the same procedure with the green wire, except insert it into hole J4.
CALIBRATION PROCEDURE 1. Set the switch to the LINE/RING position. Apply 40VDC between J1 and J2 (be sure J1 is positive), see Figure 8. Adjust R5 so that the meter reads on the line at the start of the LINE OK area. (if 40V is not available, apply 20VDC between J1 and J2, and adjust R5 so that the meter reads on the last line of the letter “N” as shown in Figure 9). 2. Switch the input voltage of J1 and J2. The (REV POL) LED should light and the meter should read within 5% of the reading in step 1. 3.
SIMPLIFIED INSTRUCTIONS Wall Jack (FOR MORE DETAIL, SEE DETAILED INSTRUCTIONS). TT-400 LINE TEST 1. Set the switch of the TT-400 to the LINE/RING position, and connect it and the telephone as shown in Figure 10. 2. Hang up the telephone connected to the TT-400. All other telephones connected to the same line should also be hung up. 3. The TT-400 meter reading should be in the LINE OK area. 4. Pick up the telephone. 5. The meter should read near zero. 6.
When hung up, the telephone should have practically no effect on the telephone line. 6. If the meter is still not in the LINE OK area with all telephones unplugged, the problem is in the line. Recheck and if necessary, remove and rewire any newly installed wires. 7. If the REVERSE POLARITY (REV POL) LED is on, the wires to the wall jack are reversed. The TT-400 will read the line voltage correctly but some telephones may not work with the polarity reversed.
telephones on the same line are also hung up. 3. The TT-400 meter should read in the LOOP OK area. If not, unplug each telephone one at a time. If unplugging a telephone causes the TT-400 meter to read in the LOOP OK area, that telephone is probably defective. 4. If the TT-400 meter still does not read in the LOOP OK area with no telephone connected, repeat steps 1 through 3 several times at 20 minute intervals to see if the problem will go away. 5.
QUIZ 1. The Central Office senses that service is being requested when . . . A - a dial tone is received. B - a current flows in the local loop. C - the telephone rings. D - a 90VAC 20Hz ringing signal is received. 2. When the telephone goes off hook, the 48VDC on the tip and ring inputs . . . A - reverse polarity. B - drops to about 0.5V. C - drops to about 1V. D - drops to about 6V. 3. A pulse dialer sends pulses spaced at . . . A - 1mS. B - 2mS. C - 100mS. D - 500mS. 4. In a tone dialer . . .
Elenco Electronics, Inc. 150 W. Carpenter Avenue Wheeling, IL 60090 (847) 541-3800 http://www.elenco.com e-mail: elenco@elenco.
