DBH 3002 and DBH 3102 (replaces the DL 800 and DL 900 but cannot work with these)
Internal calls are made with direct current signalling.  This telephone combination, DBH 3002 and DBH3102, is suitable for, e.g. in smaller offices, to arrange an external and an internal telephone connection for two devices or to relieve persons in managerial positions from phone calls, which might as well be answered by one Secretary. In the latter case, intermediate, DBH 3002, is placed with the secretary and the terminal, DBH 3102, with the manager.

The telephone DBH 3002, which has a cover of black Bakelite, contains, besides the usual parts of a automatic device, a keypad with two buttons, one red for connection of line L1 and a white for line L3, as well as an indicator to signal when L1 is in use on the end device. The device is also equipped with two signalling mechanisms, one polarized alternating current ringer mounted in a wall bracket.

Both telephones look identical and are pictured to the right.

The end device, DBH 3102, is largely similar to the intermediate, but lacks the indicator.  It is equipped with a switch for switching the AC ringer on or off.

By means of a DYY 1012 shelf, the devices can be mounted on the wall.

Line L1, which is connected to the public exchange, is connected to the intermediate apparatus. The connection between both devices require a seven-wire cable consisting of a two-wire line L2 and a five-stranded wire L3. Line L2, which was used at external calls from the end device, is connected to line L1, when the intermediate device's red button is pressed. Line L3 is used for internal calls and connect to the intermediate device when line L1 is used by the end device.  For internal calls, a local battery is required, preferably composed of three dry cells BKA 1002 or BKA 2002 which total 4.5 Volts and serves as a signal and microphone battery.  Suitable battery box for the dry cells is BKY 1002.

These devices have following function:
Calls from line L1 are received on the intermediate device, but if e.g. in the secretary's absence, the manager himself wishes to receive all incoming calls he has merely to use the switch to connect the ringer to his device, which is normally disconnected; switch of both devices power bells then ring on incoming signal; while the secretary reports an incoming call held wire L1; calls between the end device and line L1 can not intercepted in the intermediate device; conversations between the two devices can be conducted without that line L1 stores; the manager can either call management L1 directly or over management L3 request the Secretary to complete the desired call.

During a call, the intermediate device's AC ringer, the terminal AC ringer is disconnected. The microphone on the intercom was lifted off, and the red button is pressed. The device is then connected to line L1. A request needs to be made to the end device or the call must transferred there, the white button at the bottom is pressed, whereupon the end device's DC bell rings. When the button is pressed, it remains in the depressed position, but the ringing signal ceases; the white buttons on both devices must have an extra resilient bottom position for signalling. The handset on the handset was lifted, the white button is pressed and the call is answered.

During the local call, the devices are not connected to line L1, but this is kept held across one resistance. After the desired information has been obtained, the intermediate device can be connected back to the call on wire L1 by the red button, which has been in a depressed position all along, is being pushed down into bottom, triggering the white button. About the conversation in the place must be transported to the end device, pressed down the red button on this device, whereby the white button is triggered. Then the microphone on the intermediate device then hung up, both buttons and the call are triggered is connected to the end device.

Inquiry calls and transfer of calls from the end device is completed by the intermediate and takes place in a similar manner.

When calling the telephone exchange, the microphone was picked up off, after which the red button is pressed.

Dimensions:
Height 139mm, width 233mm, depth 178mm.

Weight 3.5 kg

Taken from the L. M. Ericsson Catalogue No. 610 (1939) - Swedish Translation

Circuit diagram - 215937 (DBH 31 and 33).
Circuit diagram - 215937 (DBH 3102).
Circuit diagram - 215936 (DBH 30 and 32).

DBH 3002

Last revised: May 20, 2024