RF COAXIAL CONNECTORS
In this section we will discuss about a kind of connector which is specifically designed to couple signal only, and the signal referred to the connector is nothing but the RF signals. The coaxial connectors are one of the important components of a RF system. The coaxial connectors are specially designed component for connecting and disconnecting RF transmission line to the device. The coaxial connectors are extensively used to couple RF energy from device to device since 1940s. The first coaxial connector developed was the Ultra High Frequency (UHF) connector designed by Amphenol. The coaxial connector is always cylindrical in shape and the inner metallic connector and outer metallic connector share a common axis and hence it is called coaxial connector.
The coaxial connector always found at the end of a coaxial cable. The coaxial cable is invented during 1880s and is still the best design for carrying RF energy. It has an inner copper core separated by the outer metallic shield by an insulator.
Fig. 1: Image showing structure of a coaxial cable
The coaxial connector is actually an extension of the coaxial cable maintaining the same coaxial geometry. There are wide variety of coaxial standard exist differ by their specifications. Each of them is specifically designed for particular frequency of operation, attenuation, insertion loss, environmental conditions, power handling capabilities, size, shape, strength, weight, cost etc.
Fig. 2: Image showing a coaxial connector at the end of coaxial cable
For the efficient operation of a RF system the designer should have a good understanding about the electrical specifications of the connector, since the RF energy enters or leaves the system through the coaxial connector and hence the performance strongly depends on the connector specifications. Before we move on to the discussion about different RF connectors, let us go through some of the specifications which are very significant for the RF coaxial connectors.
Characteristic Impedance
CHARACTERISTIC IMPEDANCE
A coaxial cable has an inner conductor and an outer conductor separated by insulating material between them. Any two conductors separated by an insulating material will generate a capacitance in between them, and we usually referred to such unwanted capacitance as stray capacitance. Also any conductor having significant length has an inductance. With this knowledge we can assume both the conductors in coaxial cable as continuous inductors with capacitance in between every point of the two conductors.
We are not considering the conducting materials actual resistance which is negligible, but for high frequency applications we must care for the inductance and capacitance. The equivalent of the coaxial cable transmission line having infinite length with stray capacitance and inductance is shown below:
Fig. 3: Equivalent circuit diagram of coaxial cable
At infinite length the effect of these inductance and capacitance are purely resistive, means the effect of the entire resistors and capacitors is same as the effect of a single resistor being connected to the end of the coaxial cable. Since the effect at infinite length can be considered as resistive the resistance that the coaxial cable offers to input signal is irrespective of the input frequency. We call such a resistance as the characteristic impedance of the coaxial cable.
The characteristic impedance of a coaxial cable is very important as far as a connector design is concerned, because for the maximum power transfer from the coaxial cable to the connector the connector should have exactly the same impedance of the coaxial cable.
IMPEDANCE
According to the maximum power transfer theorem the maximum power is transferred from a source to load only if the impedance of both the source and the load are same.
Fig. 4: Equivalent circuit diagram of a coaxial cable connected to a coaxial connector
In case of the coaxial cable and the coaxial connector, the maximum power from the coaxial cable is transferred to the coaxial connector only if the characteristic impedance of both the coaxial cable and the connector are exactly same. The characteristic impedance of the coaxial cable is resistive in nature and the connector’s impedance is also resistive and is represented in ohms.
Normally the coaxial connectors have impedance 50 ohms. The reason for such a value is that the connector introduces signal attenuation while passing signal from the coaxial cable to the device and the theoretical impedance corresponding to minimum attenuation for the coaxial connector of a 50 ohm coaxial cable should be 77.5 ohms. But theoretically the maximum power transfer occurs at 30 ohms, and taking the average of 77.5 and 30 we get 53.75. Rounding off the value the impedance is standardized as 50 ohm. Impedance depends on the connector geometry and insulating material parameters.
Voltage Standing Wave Ratio
VSWR
When the coaxial cable is not terminated in connector with matching impedance, it will result in ‘reflected wave’ in the cable. This reflected wave in the cable interfere with the transmitted wave and results in ‘standing wave’. Let us consider a practical experiment which help you to understand the concept of reflected and standing waves.
Fig. 5: Image showing experiment illustrating the only transmitted wave in the rope
As shown in the above figure take a rope and leave one of its ends on the ground. Lift the other end and whip it gently. You can see the waves starting from your hand travelling to the ground and dies before it reaches the ground. All the waves transmitted from your hand are lost before it reaches the ground due to the internal resistance of the rope to bending, hence no waves come back. In this case the entire energy is transmitted only and hence there is only transmitted waves exist in the rope. This state of the rope is equivalent to a long coaxial cable which is terminated in a matched impedance connector.
Now tie one end of the rope on any solid thing in such a way that the length of the rope is much shorter than the previous case.
Fig. 6: Image showing experiment illustrating the transmitted wave and reflected wave in the rope
Lift the other end parallel to the ground and gently whip the rope once. You can see the wave travelling from your hand to the solid object. If the wave is not dead before hitting the solid object it will reflect from the object and travels backward. We call such a wave as reflected wave. This state of the rope is equivalent to the coaxial cable terminated in a non-matching impedance connector.
When the waves reflect backward to the source it will interfere with the transmitting waves and results in standing waves as illustrated in the following experiment.
Fig. 7: Image showing experiment illustrating standing wave in the rope
Tie both of ends of the rope to solid objects and blew gently from one end continuously. The rope continuously absorbs the energy from one end and transmitted to the other end, which will reflect back to the same end itself. These continuously reflected waves interfere with the continuously transmitted waves producing standing waves in the string.
We have learned about transmitted wave, reflected wave and the standing wave. Now the Voltage Standing Wave Ratio (VSWR) is a measure of the effect of the standing wave in a coaxial cable. It is the ratio of the amplitude of reflected wave to the transmitted wave.
VSWR = amplitude of reflected wave / amplitude of transmitted wave
Normal connectors have a VSWR between 1 and 1.5. High VSWR values for a connector means the connector is a poor match for the 50 ohm coaxial cable. It happens due to variations in the value of impedance of the connector from the matched impedance for the cable. This impedance variation occurs due to the effect of capacitance and due to the geometry of the connector and this variation dependent on the operating frequency. Hence VSWR is usually specified in a frequency range.
INSERTION LOSS
Insertion loss is another parameter which affects the signal transmitting efficiency of the connector to the device. A significant amount of loss in amplitude occurs to the signal at the connector due to variations in impedance. The amount of such losses is called Insertion loss expressed in dB.
The insertion loss is dependents on the properties of the connector’s insulation materials and conductors.
A designer must consider the effect of insertion loss of the coaxial connector and should compensate the effect while designing the RF system.
RF LEAKAGE
A significant amount of RF energy usually radiates off from the connector itself. Due to this the signal attenuation occurs before coupling it to the device. The amount of RF energy radiated before coupling to the RF system is called RF leakage and is expressed in dB.
The RF leakage mainly occurs through the slots or holes in the connector body or it may happen due to less tight mating of the male and female connectors.
A designer must consider the effect of RF leakage of the coaxial connector also and should compensate the effect while designing the RF system.
That’s all about the common specifications found specifically in the datasheet of coaxial connectors other than the common connector specifications which we have already discussed.
Now let us find some of the common coaxial standard connectors and their details.
SMA & NEILL Connectors
SMA CONNECTOR
The SMA stands for “Sub-Miniature A”. SMA connector is a commonly used RF coaxial cable connector. It was designed by the Bendix Research Laboratories in 1958 to be used with .141 semi-rigid cables (RG-402). They are designed to operate in a frequency of 18GHz. The connector has a small diameter compared to other coaxial connectors.
Fig. 8: Image of SMA type male and female connector
The SMA connectors have threaded coupling and are made of Brass contacts separated by Teflon insulators. The SMA connectors have low reflection property, 50 ohm impedance and low VSWR. They are suitable for broad band operations and versions of these connectors are available up to 27 GHz. The SMA connectors are very strong, durable, small size and low cost coaxial connectors.
The SMA connectors can be found in amplifiers, attenuators, filters, mixers, oscillators, switches etc. The SMA connectors are widely used in military applications and RF systems including Strip Line and Micro-strip technology.
Sample specification:
Impedance —————————– 50 ohm
Frequency range ——————— 0–18 GHz
Voltage rating ———————— 500v peak
Dielectric withstanding ————- 1000V RMS
VSWR ———————————– 1.05 +
Contact resistance ——————- 2.0 milliohms
Insulation resistance —————- 5000 Megohms
RF leakage ————————— -90 db min.
Insertion loss db max. ————- .06
N CONNECTOR
The N-type connector is another connector which has proven its usefulness in RF technology.The N-type connector is in use since 1940s in RF devices. They designed to be operated in 12 GHz frequency. The name N connector is named after Paul Neill of Bell Labs who invented this connector.
Fig. 9: Image of type N male connector
Fig. 10: Image of type N female connector
It has threaded coupling interface and they usually have 50 ohms impedance. The contacts are made of Brass and are separated by insulators like Tetra-fluoride resins. The interface used in this kind of connectors is nothing but air itself. They are large in size than the SMA connectors.
The Type N connectors are used in large coaxial cables and in weather proof applications.
The N connectors are widely used in military communication equipment, microwave local area networks etc.
Sample specification:
Impedance —————————– 50 ohm
Frequency range ——————— 0–10 GHz
Dielectric withstanding ————- 1500 V AC / 1 minute
VSWR ———————————– 1.2
Contact resistance ——————- 3.0 milliohms
Insulation resistance —————- 5000 Megohms
TNC & SMC Connectors
TNC CONNECTOR
Threaded-Neill-Concelman (TNC) connectors are designed in 1956. It is specifically designed to withstand extreme vibrations. The TNC connectors are medium sized connectors which can operate up to 12 GHz.
Fig. 11: Image of type TNC male connector
Fig. 12:Image of type TNC female connector
The TNC connectors use threaded coaxial coupling. They are used in military and aerospace applications since they are designed to withstand extreme pressure and vibrations.
Sample specification:
Impedance —————————– 50 ohm
Frequency range ——————— 0–11 GHz
Working Voltage ——————— 500 Volts rms.
Dielectric withstanding ————- 1500V RMS
VSWR ———————————– 1.3
Contact resistance ——————- 1.5 milliohms
Insulation resistance —————- 5000 Megohms
SMC CONNECTOR
The SMC stands for “Sub-Miniature C” connector. It is similar to the SMB connector but it is designed for higher frequencies. Similar to other kind of connectors the SMC has 50 ohm impedance and it is designed to be operated at 10 GHz frequency.
Fig. 13: Image of type SMC male connector
Fig. 14: image of type SMC female connector
Normally Brass, Beryllium copper and copper is used as conducting materials and Teflon is used as insulating material. The SMC is identical in structure of the SMB, but it has got threads to it for threaded coaxial coupling.
The threaded structure and small size makes them suitable for operating at environments like aircrafts, space shuttle etc. They are widely used in both military and non-military applications.
Sample specification:
Nominal Impedance ——————— 50 ohms
Working Voltage ————————- 335 volts rms
Frequency Range ————————- 0 to 10 GHz
Insulation Resistance ——————– 1000 megohms min.
Contact Resistance ———————– 12 milliohms
Dielectric Withstanding Voltage —— 1000 volts rms
RF Leakage ——————————– -60 dB min
RF Insertion Loss ————————– 0.25 dB max.
MB & MCX Connectors
SMB CONNECTOR
SMB stands for “Sub-Miniature B” connector. It is designed to be operated up to a frequency of 4 GHz. Unlike other coaxial connectors it is designed for quick connect and disconnect.
Fig. 15: Image of Type SMB female and male connectors
The SMB connectors with 50 ohm and 75 ohm impedance are available. It has got an outer spring like structure for easy snap on connections. The SMB connectors are useful in environments having moderate vibrations. They are also suitable for circuit miniaturization and internal dense packaging applications. They are commonly used in PCBs with flexible cables and used in inter or intra board signal transmission.
Sample specification:
Nominal Impedance ——————— 50 ohms
Frequency Range ————————- 0 to 4 GHz
Voltage Rating —————————- 500 VRMS max.
Current Rating —————————- 1.5 amps DC max.
Insulation Resistance ——————– 1000 megohms min.
Contact Resistance ———————– 6 milliohms max.
RF Leakage ——————————– -55 dB min
RF Insertion Loss ————————– 0.30 dB max.
MCX CONNECTOR
The Micro CoaX (MCX) connector is designed and developed during the 1980s. It is specifically designed for applications where size and space savings are critical. The MCX connector is designed to be operated up to a frequency of 6 GHz. The MCX connectors are available in 50 ohm and 75 ohm versions.
Fig. 16: Image of type MCX male coaxial connector
Fig. 17: Image of type MCX female coaxial connector
The design structure of the MCX is similar to SMB, but it is approximately 30 percent smaller in size than the SMB connectors. Like SMB, the MCX connector also uses snap on coaxial connection method.
The MCX are widely used in so many commonly found microwave modules where miniaturization is very important including Global Positioning Systems (GPS), automotive, information system, communication market, cellular telephone and data telemetry
Sample specification:
Impedance ————————————— 50 ohm
Frequency Range ——————————- 0–6 GHz
Working Voltage ——————————- 335 VRMS
Dielectric Withstanding Voltage ———– 1000 Volts
VSWR ——————————————— 1.3 max. 6 GHz
Contact Resistance —————————- 5.0 milliohm max.
Insulation Resistance ————————- 5000 megohms
Insertion Loss ———————————– 0.1 dB Max.
BNC & UHF Connectors
BNC CONNECTOR
The Bayonet-Neill-Concelman (BNC) connector is named after the inventors of the BNC connector Neill and Concelman. The Bayonet is a unique coupling method used in this type of coaxial connectors. They are designed and developed in 1940s. BNC connectors are available at both 50 ohms and 75 ohm impedance versions. They are designed to operate at a maximum frequency of 4 GHz.
Fig. 18: Image of type BNC male coaxial connectors
Fig. 19: Image of type BNC female coaxial connectors
The BNC connector is identical in design with a type N connector, but it has bayonet locking mechanism for coupling. This bayonet lock provides full tight and secure mate and makes the BNC connector look totally different from other types.
The BNC connectors are used with medium sized coaxial cables and has wide varieties of applications like flexible networks, instrumentation and computer peripheral interconnections etc.
Sample specification:
Impedance ————————————— 50 ohm
Frequency Range ——————————- 0–4 GHz
Working Voltage ——————————- 500 VRMS
Dielectric Withstanding Voltage ———– 1500 Volts
VSWR ——————————————— 1.3 max. 6 GHz
Contact Resistance —————————- 1.5 milliohm max.
Insulation Resistance ————————- 5000 megohms
UHF CONNECTORS
The Ultra-High Frequency (UHF) connectors are the most popular among the coaxial connectors. It was invented at Amphenol in 1930s. Unlike all other coaxial connectors, the UHF connector has varying impedance. Due to this varying impedance the UHF connectors can be used only up to a maximum frequency of 500 MHz . They have a peak voltage rating of 500 volts. There are also Mini-UHF connectors which are small in size than the UHF connector and can be used up to a maximum frequency of 2 GHz.
Fig. 20: Image of Circular Connector
Fig. 21: Image of type mini-UHF male and female coaxial connector
Fig. 22: Image of male type UHF coaxial connector
Fig. 23: Image of female type UHF coaxial connector
Since impedance is not constant the UHF connectors are used in applications where the impedance matching is not critical. These type of coaxial connectors are very popular, economic and widely used in low cost applications like radios, public address systems etc.
Sample specification:
Impedance ————————————— 50 ohm
Frequency Range ——————————- 0–2.5 GHz
Working Voltage ——————————- 335 VRMS
Dielectric Withstanding Voltage ———– 1000 Volts
VSWR ——————————————— 1.25 max. 6 GHz
Insulation Resistance ————————- 5000 megohms
Summary
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}There are certain parameters which are significant for the coaxial connectors like impedance, VSWR, RF leakage and insertion loss
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}A good coaxial connector should have frequency independent impedance of 50 ohms or 75 ohms, VSWR nearly unity, minimum RF leakage, minimum insertion loss and higher operating frequency.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}Different types of coaxial standard connectors are available including SMA, N, TNC, SMC, MCX, BNC, SMB, mini-UHF and UHF
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}Except UHF all others have frequency independent impedance of 50 ohm or 70 ohm.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}The coaxial connector with highest operating frequency is SMA connector with a maximum frequency of 27 GHz and the coaxial connector with lowest operating frequency is UHF connector which can be operated below 500 MHz only.
CPC & DIN Connectors
CPC CONNECTOR
The Circular Plastic Connectors (CPC) are designed and developed during 1970s. As the name indicates they are made mostly of plastic except the metal contacts. They are circular in shape and designed for reliability. The CPC connector is considered as an industrial standard power and IO connector. They are available in free-hanging or flanged housing and PCB mountable versions. The CPC connector family includes all kind of connectors like wire-to-wire, wire-to-board, power connectors, IO connectors and even coaxial connectors.
Fig. 24: Image showing different varieties of CPC connectors
The circular geometry allows more space saving method of arranging the contacts. Compared to any of the rectangular connector, the same number of pins can be arranged in the CPC connector in a much smaller space. The wires can be assembled to the CPC using crimping and soldering methods.
Fig. 25: Image of male CPC
Fig. 26: Image of female CPC
The CPC are made of lightweight, stabilized, heat resistant, self-extinguishing, high impact thermoplastic materials. Most of them are polarized connectors. They provide easy connect and disconnect capability. The parts of the connectors including pin, receptacle etc. can be easily disassembly and hence provide quick repair. Some CPC comes with even color codes. The CPC can be used for coupling both signal and power and some of the CPC connectors having maximum current rating of 50 amperes.
The CPC connectors are suitable for applications where the size, contact densities are critical like industrial, instrumentation, transportation etc. They are widely used in industrial machinery, factory automation, material handling equipment. They are suitable for Rail and Transit vehicles and systems, Medical Instrumentation & Equipment. The CPC connectors are widely used in all kind of Communication equipment, networking, data storage, computers & peripherals. The small size and light weight of the CPC connectors make them ideal connectors for Aerospace and defense equipment and systems.
Sample specification:
Current Rating ———————————- 4 ampere
Dielectric Withstanding Voltage ———– 1650 Volts
Contact Resistance (milliohms) ————- < 5 mille ohm
Insulation Resistance ————————- 5000 megohms
Summary
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}The name CPC stands for Circular Plastic Connector.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}As the name indicates they are circular and made of plastic except the metal contacts
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}Almost all kind of connectors are available in this family of connectors
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}The advantage of circular shape is that it can house large number of contacts in a small space
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}The advantage of plastic is light weight, durability, easy assembly and repair.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}They can be used for transmitting both signal and power.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}Connectors are available with maximum current rating of 50 amperes.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}They are industrial standard power IO connector and are widely used in all kind of devices.
DIN CONNECTOR
The name DIN stands for “Deutsches Institut für Normung” which is a German standard organization who standardize this connector. The DIN connector is also a member of circular connectors. There are different standard connectors under the DIN connector standard. All the DIN connectors having same diameter, but the number of pin differ with the DIN standard. The known DIN standards are DIN41524, DIN41612, DIN43356, DIN41652 etc. The number of pin varies from 3 to 15 keeping the outer diameter of the connector same. Standard DIN connectors are available in pin format as shown in the following image.
Fig. 27: Diagram of the different DIN connector standards
The DIN connectors use round push-fit mating method. The DIN connectors are polarized connectors with a notch in the shell ensuring that the pins will connect only in the correct orientation. It also prevents the mating of incompatible connector types damaging their pins. The wires are attached to the pins of the DIN connectors by soldering.
Fig. 28: Image of 7-pin DIN male and female connector
Irrespective of their pin numbers the pin position in the DIN connector remains the same. Different pin numbered DIN connectors are used for different applications.
The DIN connectors are used as SYNC and MIDI interface in musical instruments, amateur radios, serial ports, PS/2 keyboard and mouse connector etc.
Let us take a look at the different pin-outs and other details of the DIN connectors used in different applications.
Loudspeaker (2 pin)
DIN connectors with two pins are used for connecting wires to the loudspeaker. The image of the 2 pin male loudspeaker DIN connector is shown below.
Fig. 29: Image showing pin position of two pin DIN connector
The pin-out of the 2 pin DIN connector
PIN 1 ——————POSITIVE
PIN 2 ——————NEGATIVE
Microphones (3 pin)
The three pin DIN connectors are widely used in microphones. They are similar to the XLR standard connectors but not compatible with them. The three pin DIN connectors are used in balanced, unbalanced, dual impedance microphones. The pin position of 3 pin DIN connector is viewed from the solder side of the plug is shown in the following figure.
Fig. 30: Diagram of DIN connector
Pin position of three pin DIN connector
The pin-out of the 3 pin DIN connector for balanced microphone
PIN 1 ——————LIVE
PIN 2 ——————SCREEN
PIN 3 ——————RETURN
The pin-out of the 3 pin DIN connector for unbalanced microphone
PIN 1 ——————MONO INPUT
PIN 2 ——————SCREEN
PIN 3 ——————NOT CONNECTED
The pin-out of the 3 pin DIN connector for dual impedance microphone
PIN 1 ——————MONO INPUT HIGH
PIN 2 ——————SCREEN
PIN 3 ——————MONO INPUT LOW
5 pin DIN
DIN connectors with five pins are used in applications like stereo microphone, tuners, headsets, etc. The pin position of 3 pin DIN connector is viewed from the solder side of the plug is shown in the following figure
Fig. 31: Diagram of 5-pin DIN connector
Pin position of five pin DIN connector
The pin-out of the 5 pin DIN connector for stereo microphone
PIN 1 ——————LEFT INPUT
PIN 2 ——————SCREEN
PIN 3 ——————NOT CONNECTED
PIN 4 ——————RIGHT INPUT
PIN 5 ——————NOT CONNECTED
The pin-out of the 5 pin DIN connector for tuners
PIN 1 ——————LEFT INPUT
PIN 2 ——————SCREEN
PIN 3 ——————LEFT INPUT
PIN 4 ——————RIGHT INPUT
PIN 5 ——————RIGHT INPUT
The pin-out of the 5 pin DIN connector for headsets
PIN 1 ——————NOT CONNECTED
PIN 2 ——————LEFT OUTPUT
PIN 3 ——————RIGHT OUTPUT
PIN 4 ——————LEFT OUTPUT
PIN 5 ——————RIGHT OUTPUT
MINI DIN CONNECTOR
MINI DIN & XLR Connectors
The DIN connectors comes in a miniature model called Mini DIN connector. They are smaller than the standard DIN connectors and also their pin position varies from the DIN standard.
Fig. 32: Image of Male andd Female Mini DIN connectors
Mini DIN connectors are available from 3 pin up to 9 pin contacts. The Mini DIN connectors are used as a standard connector for PS/2 protocol devices. They are also used as connectors in SVHS video equipments.
4 pin mini DIN
Four pin mini DIN connector is used as a cable connector for SVHS video system. The pin position for a four pin DIN connector viewed from solder side of the plug is shown in the following figure.
Fig. 33: Diagram of 4-pin Mini DIN connector
The pin position of a 4 pin SVHS connector
The pin-out of the 4 pin mini DIN connector for SVHS video system
PIN 1 ——————LUMINANCE GROUND
PIN 2 ——————CHROMINANCE GROUND
PIN 3 ——————LUMINANCE/INTENSITY (Y)
PIN 4 —————-CHROMINANCE/COLOR (C)
PS/2
IBM Personal System 2 (PS/2) is a communication protocol used to interface mouse and keyboard with personal computers. Six pin mini DIN connectors are defined as standard connectors in this protocol. They are designed to replace the old RS232 standard keyboard and mouse interfacing method in personal computers.The mini DIN connectors used for connecting the mouse and the keyboard are electrically identical, but should not be interchanged while connecting. The Keyboard port can be identified by its purple color and the mouse port can be identified by its green color.
The pin position of a 6 pin female mini DIN connector viewed from solder side of a plug is shown in the following image.
Fig. 34: Diagram of PS/2 connector
The pin position of a 6 pin PS/2 connector
The pin-out of the 6 pin mini DIN connector for PS/2 devices
PIN 1 ——————DATA
PIN 2 ——————NO CONNECTION
PIN 3 ——————GROUND
PIN 4 ——————VCC
PIN 5 ——————CLOCK
PIN 6 ——————NO CONNECTION
Sample specification:
Current Rating ———————————- 1 ampere AC
Voltage Rating ———————————- 100 V
Dielectric Withstanding Voltage ———– 1650 Volts
Contact Resistance (milliohms) ————- < 5 mille ohm
Insulation Resistance ————————- 5000 megohms
Summary
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}DIN is a circular connector with pin number range from 3 to 15
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}They are polarized connectors
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}DIN connectors are mostly used in audio applications
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}PS/2 standard connector is a mini DIN connector with 6 pins.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}6 pin mini DIN connectors are used for connecting PS/2 keyboard and mouse
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}4 pin mini DIN connectors are used in SVHS video system
XLR CONNECTOR
The XLR is a kind of circular connector commonly found in audio, video devices like microphone, intercom etc. The XLR connector is designed by James H. Cannon from California. The connector he invented was commercially produced and named after him as Cannon ‘X’ connector and later a latch version has been released. The latch stands for the ‘L’ and the ‘R’ stands for resilient polychloroprene which was used as a material surrounding the female contacts. The XLR connectors are available from 2 pin to 9 pin contact connectors.
Fig. 35: Image of a 3-pin male and female XLR connector
From the above image of the 3 pin XLR connector, you might have noticed the latch on the female connector. This feature in the design of the XLR connector is a locking mechanism for avoiding loose contacts of the male and female connector. Also one of the three pin are longer than the other and it is designed in such a way that the longer pin makes contact before the others does. This pin is used to make ground contact before the signals contacts are made.These connectors are very similar with the design of the DIN connector but are not compatible with each other. The XLR connectors are available in both cable and chassis mountable models.
The XLR connector is commonly used with all kind of electrical connector especially in professional audio with balanced audio interconnection, including AES3 digital audio, video, low-voltage power supplies, stage lighting equipment etc.
XLR with different pin numbers are used for different applications. Let us take a look at the application and pin-out of the commonly used XLR connectors.
3 pin XLR
The three pin XLR connectors are found in almost all kind of professional microphones. They are also used as connectors for loudspeaker cables. The pin position for the three pin male XLR connector is shown below.
Fig. 36: Diagram of 3-pin XLR connector
The pin position for a three pin XLR male connector
The pin-out of the 3 pin XLR connector for microphone
PIN 1 ——————GROUND
PIN 2 ——————POSITIVE/BALANCED AUDIO
PIN 3 ——————NEGATIVE/BALANCED CIRCUIT
4 pin XLR
The four pin XLR connectors are commonly used with talk back headset, unbalanced microphone, analog lighting control, DC power connections etc. The pin position for the four pin XLR male connector is shown in the following figure.
Fig. 37: Diagram of 4-pin XLR connector
The pin position for a four pin XLR male connector
The pin-out of the 4 pin mini DIN connector for a talk balk headset
PIN 1 ——————MIC GROUND
PIN 2 ——————MIC SIGNAL
PIN 3 ——————EARPHONE EARTH
PIN 4 ——————EARPHONE GROUND
The pin-out of the 4 pin mini DIN connector for an analog lighting control device
PIN 1 ——————SCREEN
PIN 2 ——————CLOCK +
PIN 3 ——————ANALOG MULTIPLEX
PIN 4 ——————CLOCK –
Sample specification:
Current Rating ———————————- 15 ampere AC
Voltage Rating ———————————- 1400 VRMS
Dielectric Withstanding Voltage ———– 1650 Volts
Contact Resistance (milliohms) ————- < 3 mille ohm
Insulation Resistance ————————- 1000 megohms
Summary
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}XLR is a kind of circular connector commonly used in professional microphones
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}They are similar to DIN but not compatible and they have a latch mechanism
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}They are available from 2 pin to 9 pin contacts
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}2 pin XLR is used in DC power connectors, 3 pin for microphone, 4 pin for intercom, 5 for light control, 6 pin for dual channel intercom, 7 pin for microphone with power supply etc.
{C}{C}{C}{C}{C}{C}· {C}{C}{C}{C}{C}{C}Irrespective of the above said applications they are widely used in electrical and electronic devices with user defined pin-outs.
In this tutorial, we learnt about the circular connectors and we have seen RF coaxial connector which is designed for high frequency signal transmission, CPC connector designed for all kind of power or signal or both, DIN and XLR which are primarily designed for audio applications.
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