•  
  •  

Having secrecy in parallel telephones

Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their proper performance, such as overloading and overhearing of the conversation by an undesired person. In order to eliminate all such problems and get a clear reception, a simple scheme is presented here (Fig. 1).
This system will enable the incoming ring to be heard at both the ends. The DPDT switch, installed with each of the parallel telephones, connects you to the line in one position of the switch and disconnects you in the other position of the switch. At any one time, only one telephone is connected to the line. To receive a call at an end where the instrument is not connected to the line, you just have to flip the toggle switch at your end to receive the call, and act as usual to have a conversation. As soon as the position of the toggle switch is changed, the line gets transferred to the other telephone instrument.
Mount one DPDT toggle switch, one telephone ringer, and one telephone terminal box on two wooden electrical switchboards, as shown in Fig. 3. Interconnect the boards using a 4-pair telephone cable as per Fig. 1. The system is ready to use. Ensure that the two lower leads of switch S2 are connected to switch S1 after reversal, as shown in the figure.

If there are any problems please contact webmaster@electronic-circuits-diagrams.com

Please share & like

WESTINGHOUSE CNC CORE MEMORY BOARD 8205D32G01 - USED - 30 DAY WARRANTY
$400.0 WESTINGHOUSE CNC CORE MEMORY BOARD 8205D32G01 - USED - 30 DAY WARRANTY picture
BENDIX DYNAPATH ARC5 CORE MEMORY 2 BOARD P/N: 3725536J - USED - 30 DAY WARRANTY
$250.0 BENDIX DYNAPATH ARC5 CORE MEMORY 2 BOARD P/N: 3725536J - USED - 30 DAY WARRANTY picture
SIEMENS 6FX1817-0AX16 MEMORY MODULE *USED*
$185.0 SIEMENS 6FX1817-0AX16 MEMORY MODULE *USED* picture
Intel D8155H 2048-Bit static memory
$7.0 Intel D8155H 2048-Bit static memory picture
HP/Agilent 35670A Option UFC Add 8 megabyte memory
$200.0 HP/Agilent 35670A Option UFC Add 8 megabyte memory picture