Common switch

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A device for multiple use of a subscriber line (formerly " exchange line") with usually two phone numbers (two-way line, multiple line or shared line ) is referred to as a shared switch ( GUm ) . In the analog telephone network , these two-way connections were assigned due to a lack of lines. These connections were often far from the central office .

He switches the outside call to the terminal assigned to the respective call number. It also switches the terminal to the exchange line as soon as the hook switch of the telephone set is activated (i.e. the telephone receiver is lifted). Other terminals are inactive as long as the devices connected to the same GTo participants can not call each other therefore. The shared switch is connected to a shared transmission (GAsUe) in the exchange , which also supplies it with electricity. Therefore it does not need a power supply on site. In relay technology , they were available as an additional box with two latching relays and later as an electronic assembly in the junction box in front of the end device.

Shared lines are no longer used in the Deutsche Telekom telephone network .

Designs

Common switch 1/2 GUm 53 from SEL (Standard Elektrik Lorenz)
Shared switch 1/2 GUm 58.1
Common changeover switch GUm 1/10
  • 1/2 GUm 39
  • 1/2 GUm 53
  • 1/2 GUm 58
  • 1/2 GUm 59 (only in the Deutsche Post area)
  • 1/2 GUm 70 (only in the Deutsche Post area)
  • 1/2 GUm 90 (only in the Deutsche Post area)
  • 1/10 GUm (only in the Deutsche Post area)
  • 3/10 GUm (only in the Deutsche Post area)
  • Two-way connection ZA68 (Austria)

The name of the common switch in Germany consists of:

  • 1/2 = 1 exchange line / 2 subscriber lines, each with its own phone number
  • GUm = shared switch
  • Year (19xx) of the construction

General

The older two-way connections (1/2 GUm 39) show small defects in some parts, which prevent the general use of two-way connections. In the old shared changeover switch, the turnout relay, which is located with its windings in the voice wires, causes additional losses (damping, loss of supply current). The old switch interrupts the line loop immediately after the calling subscriber hangs up. The charge pulse for a charge indicator to display the units was at a local call sent only after you hang up the phone and could not therefore be used.

Another peculiarity was that the alarm clock of the participant who was not involved in the conversation sounded quietly due to the charging and discharging of the capacitors as soon as the other participant picks up or hangs up.

The old circuit of communal transmission has the disadvantage that locking a single intercom and switching to the special telephone services is only possible by unsoldering and isolating individual relay contacts. All these disadvantages of the switch and the transmission have been avoided by using new components. The latching relay was introduced in the new switch (1/2 GUM 53). The latch relay remained activated after hanging up the phone and the charge impulses after the call could be transmitted.

Individual evidence

  1. ↑ Handbook of Telecommunications Technology, Volume 7, Part 2, Line Technology, as of spring 1980, p. 93
  2. ↑ Handbook of Telecommunications Technology, Volume C5, Wählvermittlungstechnik, 1970, p. 105

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