Vintage Hella Police Fire Alarm Signal switch clock

Vintage Hella police fire department Alarm Signal sequence switch clock in very good condition.
This rare switch is working very well. It was mounted in the 50ies in German police, fire and ambulance VWs like VW Oval Bug and T1 Fire bus. It works like an egg clock. When the sequence switch is on, the high low fanfare horns are on.

The chrome is dirty but very good and without dents. The knob is very good and working. The case is also good and without dents. Even the 2 small black rubber pieces are on the rear for cable protection. In total is looks like new old stock. The rear diameter is 5,5 cm, the front face diameter is 6,5 cm and the knob diameter is 4,0 cm.

The last picture shows the switch in the Hella parts catalog from 1954. The name in German is "Schaltautomat" and Hella made three different versions. The switch for sale is Hella # 91/31. It has on the chrome face number 1, 2, 3, 4. Depending on the setting the fire or police signal runs 1 to 4 times.
You can connect 3 cables to the switch. One ground cable and behind a cover are 2 screw terminal connectors which are marked on top of the cover with “H” and “T”.
H is in German for “hoch” for the high tone horn wire, e.g. for a 520 hz horn.
T is in German for “tief” for the low tone horn wire, e.g. for a 390 hz horn.

I tested the switch very simple with 1x battery, 2x bulb and the 1x Hella switch:
-Bulb 1: Bulb Ground cable (-) to Hella Switch “H / HOCH”. Bulb Power cable (+) to Battery (+)
-Bulb 2: Bulb Ground cable (-) to Hella Switch “T / TIEF”. Bulb Power cable (+) to Battery (+)
-Hella Switch: Hella Switch Ground cable (-) to Battery (-)
-I then used the switch and the lights of the bulbs was switched on and off in a certain sequence.

If you put horns behind the switch, you will listen to the special police fire department sound. So cool! A very nice to have accessory.

Please note that if you want to use the switch with two horns, you need also two relays. As you can see on the last picture, Hella sold relays called “Doppel Relais für Polizei, Feuerwehr mit Schaltautomat”. These are the special relays for the Hella alarm Signal sequence switch.