Impulse indicator

Impulse identification ( IKZ ) is an old signaling method of the German telephone network . It was used between electromechanical exchanges (for example System 50 ) for long-distance dialing and for analog telephone lines for telephone systems with direct dialing . Direct current pulses were used to transmit the signaling information.

AC transmission for walking traffic

In the local networks, direct current signals were used as permanent signals due to the three-wire galvanic connection of the individual selection levels. In the long-distance dialing technology, the DC blocking of the line and also the carrier frequency technology made these permanent signals impossible, because permanent signals cannot be transmitted in a circuit blocked by a transformer .

As a precaution, the impulse indicators (IKZ 50) were introduced by the dialing system 50.

List of pulse indicators

The following table only shows the characters used and their length at the exchange through the internal signaling or on the trunk line.

character	FernVst		Pipeline	comment
meaning	Signal on wire	Length in ms	Signal wire: out band Length in ms
Forward sign
Occupy	+ c	Permanent sign	40
Number dialing (pulse / pause)	+ a	60/40	40/60
Trigger	+ c turn off	Permanent sign	400 1600	with carrier frequency transmission with alternating current transmission
Backward sign
Retrieval	+ e	150	150
End of election	+ b	175	175
Start sign	+ b	175	175
Final character (impulse / pause)	+ b	175/450	175/450
Busy	+ b	750	750
Trigger acknowledgment			750	at TFUe, FGS, WS
Lock (pulse / pause)	- Turn off c	Duration	Duration 150/450	at WUE at TFUe
counting	- e - b	140 140	140 140	with 4-wire line with 2-wire line
Special characters
Remote license plate	+ b	40	+ b 40	any 2-wire transmission
Undamping	- a	Duration

The individual characters had the following meanings:

Occupancy code

The next following switching element was assigned the assignment code.

Dialing characters

The dialing signal sent the digit just dialed as a direct current pulse.

Trip sign

The trigger signal ended the assignment and released the following switching element again.

Call mark

The call mark was only exchanged between registers and caused the removal of the remaining digits that were stored in the previous register.

End of election sign

End-of-dial characters were only generated in networks with phone numbers of different lengths. If the call number of the called subscriber was fully recognized in the destination, it led to the quickest possible shutdown of the complex and expensive registers in indirectly controlled systems.

Start sign

The start signal was generated when the called subscriber picked up the handset and initiated the beginning of the obligation to charge for a call in the zoning exchange. That was usually in the central exchange (KVSt).

Final sign

The end signal was sent by the line selector of the called subscriber. It was sent as a flicker to the counting pulse generator (ZIG) in the KVSt. If the calling subscriber did not hang up, the connection was usually released after 90 seconds. This prevented a permanent counting of the fees. It also enabled the called subscriber to block and released the trunk lines again. This sign was initially only evaluated in long-distance traffic. Since the introduction of the local service, it has also been evaluated in local traffic.

Busy signal

The busy signal was issued by every input switching element when the connection was established, if the following switching stage or the following selector could not be reached because all accessible outputs were occupied. In this case it had the meaning of a "busy alley". If the busy signal arrived after the end-of-election signal, it had the meaning of a busy subscriber.

It was evaluated in the zoning VSt (usually KVSt) and led to the automatic forward tripping of the following switching elements. The switching elements and long-distance line were immediately released and the busy tone on the pulse generator in the KVSt was applied to the subscriber line.

Trigger acknowledgment

The release acknowledgment was only exchanged between the incoming and outgoing transmissions of a trunk line section as an acknowledgment of the release signal. In the event of an error in the acknowledgment, the triggering was repeated and should also release the section again if a trigger symbol was missing.

Lock sign

The blocking signal was sent by the incoming transmission (Ue-k) when the following switching element could no longer be assigned. This could be technical malfunctions or an operational manual lock. On the outgoing transmission (Ue-g), it meant that the long-distance line could no longer be occupied, thus avoiding unnecessary blind traffic and disruptions in the network.

Counters

The counting signal was given over long-distance lines from the zoning VSt via the 1st group selector to the charge counter of the calling subscriber.

Remote license plate

The remote identifier was applied to the b-wire during the transition from the long-distance network to the last transmission with each first pulse of a dialed digit. In connection with the line voter (end-of-election signal as permanent signal), it caused the generation and transmission of the end-of-election signal. In telephone systems with direct dialing, it could be evaluated to differentiate between local and long-distance calls.

Damping indicator

The attenuation signal was only exchanged within long-distance exchanges with a transition from a 2-wire to a 4-wire line or from a 4-wire to a 2-wire transmission between the two outgoing and incoming transmissions involved. Depending on the circumstances of the transmission plan, the attenuation signal in the 4-wire transmission caused the extension line to be switched off with a value of 3.5 dB (use of the gain reserve of the 4-wire circuit). In a 2-wire transmission, an additional extension cable (adjustable from 0 to 3 dB) was switched on for reasons of stability.

See also

• Main connection identifier

Individual evidence

1. ↑ FTZ guideline 1R3 (historical)
2. ↑ Handbook of Telecommunication Technology, Series, Volume V - Switching Technology Part 1

Web links

• Technical information on the pulse indicators