Automatic telephone for one local and one exchange line

DL 800

Intermediate telephone for use in conjunction with DL 900.

This telephone is designed to work in conjunction with DL 900; DL 900 should be installed in the manager's room and DL 800 in the room of his secretary. The telephones have been designed with a view to relieve the manager from calls which can be answered by the secretary.

The line from the telephone exchange is connected to both instruments, and each instrument has an AC bell for receiving the signals. The manager's telephone, DL 900 has a key for disconnecting the bell, and the secretary's telephone DL 800 has an indicator for indicating when the manager's telephone is in connection with the exchange line.

For local communication between the two telephones there is a separate two wire line, which is connected to a DC bell in each instrument. Each instrument has two press buttons, one red for connecting the exchange line and one white for connecting the local line.

One battery is required for the local line and this battery should be placed at the secretary's instrument. The battery may suitably be made up of dry cells and is used on local calls both for transmitter supply and for signalling by means of the DC bells. 3 cells of l.5 V each will in most cases be sufficient. Should the distance between the instruments be so great that the voltage is insufficient for signalling, additional dry cells may be inserted.

An installation comprising these telephones has the following advantages:-

  1. calls from the exchange line are received by the secretary's telephone, but, if, for instance in the secretary's absence, the manager should want to answer all incoming calls he has simply to connect the bell of his telephone which will usually be kept disconnected. The bells of both instruments will then ring on incoming calls;
  2. when the secretary reports an incoming call the exchange line is held;
  3. conversations between the manager's telephone and the exchange line cannot be overheard in the secretary's telephone;
  4. local calls between the two telephones can be carried on without disturbing the exchange line;
  5. the manager can either call the exchange line direct or use the local line for instructing the secretary to set up the connection wanted;
  6. false calls are prevented by the lines being connected only after the handset has been lifted and one of the buttons pressed.

Incoming calls are operated in the following manner:
on incoming calls the bell of the secretary's telephone (A) rings; the bell of the manager's telephone (B) being usually disconnected. The handset of the telephone A is lifted and the red button of this telephone is pressed. The secretary will then be in connection with the exchange line. The secretary then presses the white button in bottom position and in this manner gives a signal to telephone B. When the button is released it remains in pressed position but the ring signal ceases, the white buttons of both instruments having an extra self restoring bottom position for signalling. The red button remains pressed and the exchange line is held. The manager presses the white button of telephone B and answers the secretary's call; he can then take over the call on the exchange line by pressing the red button of telephone B which will restore the white button. When the secretary replaces the handset of his telephone both press buttons will be restored. The manager will then be in connection with the exchange line.

Should the manager want to transfer a call to the secretary this may be carried out in the following manner; the manager presses the white button of telephone B and thus sends a signal to the secretary. The red button remains in pressed position and the ex change line is held. The secretary answers the manager's call by lifting the handset and pressing the white button of his telephone. The secretary can take over the call by pressing the red button and will thus come in connection with the exchange line. When the manager replaces the handset of his telephone, the two press buttons will be released.

This telephone may be used as a wall set by means of a bracket RK 5010.

Dial RG 112, dial cord RS 5062, DC bell RA 610/4.5, 40 ohm, for the local line, micro-telephone RE 1041 of black Bakelite with removable capsule transmitter RC 4000/200, 200 ohm, and cord RS 5080, condenser RI 654, 2 uF, condenser RI 260, 1 uF, indicator 100 ohm, 2 press but tons, 1 red and 1 white, case of black Bakelite. bell box with 1000 ohm polarized AC bell for the exchange line, condenser RI 260, Instrument cord RS 9951. line terminals, cover of black enamelled sheet iron.

Height 140 mm, width 233 mm, depth 175 mm, weight with bell box 3.6 kg.

Taken from the L. M. Ericsson Telephones and Signalling Material Catalogue No. 188 (1934)


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Last revised: November 06, 2022