GB850861A - Improvements in or relating to telephone bell ringing circuits - Google Patents
Improvements in or relating to telephone bell ringing circuitsInfo
- Publication number
- GB850861A GB850861A GB3254755A GB3254755A GB850861A GB 850861 A GB850861 A GB 850861A GB 3254755 A GB3254755 A GB 3254755A GB 3254755 A GB3254755 A GB 3254755A GB 850861 A GB850861 A GB 850861A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bell
- ringing
- exchange
- transistor
- line
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M19/00—Current supply arrangements for telephone systems
- H04M19/02—Current supply arrangements for telephone systems providing ringing current or supervisory tones, e.g. dialling tone or busy tone
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Devices For Supply Of Signal Current (AREA)
Abstract
850,861. Automatic exchange systems. POSTMASTER GENERAL. Nov. 14, 1956 [Nov. 14, 1955], No. 32547/55. Class 40 (4). A subscriber's bell BL is fed from an exchange battery B connected to the subscriber's line on the outgoing side of exchange switches ECS, a ringing signal being sent from a ringing generator RG at the exchange over the exchange switches to control the ringing of the bell BL by power from the exchange battery B. The arrangement is particularly intended for use with electronic exchanges, in which the switches are not suitable for the transmission of sufficient power to operate a conventional bell. As shown, a capacitor C1 in series with a magneto bell BL is normally charged to the potential of the exchange battery B. The ringing signal (audio-frequency modulated at a low frequency) is received by a tuned circuit C3, T2, demodulated by MR, C4, and applied to the emitterbase circuit of a transistor TS so as to increase the conduction between the emitter and collector which are bridged across the capacitor C1 and the bell BL, thus ringing the bell. The current drawn from the exchange battery varies the potential of a lead 4 to give a check signal to the exchange that the ringing is effective. Distortion of speech transmission by C3, T2 may be reduced by shunting the transformer T2 by a resistor R4 under the control of additional cradle-switch contacts CS3. Alternatively the cradle-switch may disconnect the circuit C3, T2 from the line. Instability due to feed-back at the transistor TS is prevented by a resistor R 1, which may be replaced by the emitter-collector path of a second transistor, Fig. 2 (not shown). In a modification (not shown), a D.C. bell is used with a series-connected transistor. Selective ringing on a party line may be effected by using different audio-frequencies for the ringing signals. A thermistor in series with the bell prevents tinkling due to dialling by another subscriber on the line.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3254755A GB850861A (en) | 1955-11-14 | 1955-11-14 | Improvements in or relating to telephone bell ringing circuits |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3254755A GB850861A (en) | 1955-11-14 | 1955-11-14 | Improvements in or relating to telephone bell ringing circuits |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB850861A true GB850861A (en) | 1960-10-12 |
Family
ID=10340280
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB3254755A Expired GB850861A (en) | 1955-11-14 | 1955-11-14 | Improvements in or relating to telephone bell ringing circuits |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB850861A (en) |
-
1955
- 1955-11-14 GB GB3254755A patent/GB850861A/en not_active Expired
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