Propose a scheme telephone, which has the following distinctive properties compared with the widely known [1]:
- in the call device is a high voltage coupling capacitor, and it is constantly included in the loop of the telephone line;
- use as a microphone and telephone amplifiers circuits KUN (analog MS) allowed to reduce to a minimum the number of elements in the "binding" spoken node.
This phone allows you to take the challenge and to have a conversation. It can be used for kitchen, bathroom rooms etc can be Placed in the body of children's toys, in a case from a toothbrush. If desired, the circuit can be supplemented and dialer. Chip call TO AP 1 (analog DBL5001/2) is enabled by standard the schema. The only difference is in the power circuit of the chip is included the Zener diode VD2 voltage stabilization 82 V. Thanks to him calling device is not bypasses the telephone line for dialing and conversational connection.
Spoken node is assembled on a chip D2 and D3. Capacitor C3 and resistor R6 is the power supply filter for microphone WM. C7 - locking. Load IC D2 is a resistor R8. Scheme suppresses local effect. Adjustment is performed by resistor R9.
With stable parameters of R5, VM, R7, R8, a resistor R9 can be replaced by two constant resistor. The magnitude of the signal for the phone BF1 is set by resistor R10. Chip D3 powered from parametric stabilizer R6-VD5-C5. Capacitor C8 - locking.
Because of the simplicity and good reproducibility of this scheme can be used to improve on older handsets.
Note. In the diagram, the pin 7 of the chip D2 must be connected to the output 6 chip D3. The resistor R6 in the circuit parametric stabilizer (as erroneously indicated in the text) is not included.
Literature
1. Kisluk A. I. Handbook of the device and repair of telephones domestic and foreign production. - M.: Biblion, 1997.
Author: A. Mikhalevich, Minsk, RL 12/98; Publication: N. Bolshakov, rf.atnn.ru