Common battery
When speaking circuit is a term used landline phones the technical execution, the speech circuit power supply ( microphone power supply ) of the stations (telephones ).
Was used for voice transmission in the early days of telephone technology of Bell's telephone. In this only one component for speaking and listening was used. Speaking an induction voltage (voice AC voltage ) is generated which was transferred via a line to the remote station; a separate power supply was not available. This form of transmission was no longer sufficient in terms of range and quality of understanding soon with the requirements. There telephones ( telephones ) with separate components for speech ( microphone) and listening ( Fernhörer ) have been developed. For the operation of the microphone, a power supply is required. In the operation of the development on the use of an erected at the subscriber's battery led ( " local battery "; OB- operation) to centrally " in office " placed battery ( " Central Battery "; ZB- operation). In order for the microphone is supplied with the battery voltage, the remote handset is not crossed by the direct current, a corresponding intercom circuit is depending on the mode the telephone ( " station " ) is required. When using a local battery Speak of the OB- operation and of the OB -Intercom circuit in the central battery from the ZB- operation and of the ZB- speaking circuit.
- 2.1 CB Communication circuit
- 2.2 W -Intercom circuit
- 2.3 application
- 2.4 development
OB- operation
When OB- operation, the voltage source is to power the microphone in place, ie the participant. In the line is not DC, but rather only the inductively transmitted to the line opening AC flows. A disadvantage of the OB- operation in comparison with the example of the operation is greater technical complexity in the station, and the need to have to operate at each station a high-maintenance voltage source.
LB-communication circuit
In the LB-communication circuit, the microphone of the console ( telephone ) is inductively in a particular circuit, using a transformer coupled to the line. The remote handset is in the conduit.
Scope
Public telephone networks were operated in the early days of telephony in the OB - operation. Today OB phones are still considered as so-called field telephones in the military (for example, Federal Armed Forces), civil protection associations (for example, Technical Relief ) and used as distance remote speaker at the ÖBB.
For example, operating
When ZB- operation, the voltage source is to power the microphone at a central location, generally in the switching device. Speaking flows superimposed with speech ac dc current in the line. The speaker AC is transmitted inductively to the receiver circuit.
For example, intercom circuit
The ZB intercom circuit, the microphone of the console ( telephone ) is on the line. The remote handset is in a particular power circuit inductively, by means of transformers, coupled to the line.
Wireless intercom circuit
With the introduction of Selbstwählverkehrs an extension of the ZB- speaking circuit was required. The W -Intercom circuit differs from the ZB- speaking circuit, characterized in that in the telephone sets a component to select ( number switches, keypads) is installed. The production of the desired compound is no longer manually switching, but through a switching device. The original basic circuit for ZB- operation does not change; it merely is the additional Wählbauteil.
Scope
All Public telephone networks in the fixed network working principle in ZB- operation.
Development
Since the 1920s, a special transformer with a specially wound primary coil is used: This consists of two oppositely wound coil windings with a center tap. Since in the present circuit, the microphone is connected between line and center tap, distinguished by the oppositely wound primary coil, the signal of its own microphone for the most part on ( sidetone suppression ), while the other party is still audible through the telephone speaker. This sidetone was subjected to in the 1960s by switching of capacitors and resistors to continuous development. Since the late 1980s, the transformer is simulated by resistance bridges in conjunction with electronic IC amplifier circuits.