Caller ID based on PANASONIC KX-T2365 phone. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Caller ID based on PANASONIC KX-T2365 phone. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Telephony

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Our magazine has already talked about telephones with automatic identification of the caller's number (AON) and telephone set-top boxes developed by Telesystems. Today we will talk about adding caller ID functions to the Panasonic KX-T2365 telephone.

It is known that most phones with caller ID are made on the basis of cheap Asian-made devices. But firstly, such phones are not very decent to put in the office, and secondly, their mechanical elements are not very reliable. It's still acceptable to have a phone like this at home where it's not heavily used, but if you use the phone all day long, its keys start to function fuzzy after a while. From this we can conclude that caller ID, which will not spoil the interior with its appearance and daily long work with which will not cause a headache, should be based on telephone sets of firms known for their high quality.

One of the most common modern telephones in Russia is "Panasonic KX-T2365". Well thought-out design, reliability, presence of the liquid crystal indicator do it attractive to buyers.

Therefore, it is quite natural to want to add caller ID functions to this device. This idea was implemented by Telesystems. A small board is built into the phone, which performs the functions of caller ID. In this case, all functions of the base telephone are retained.

An additional fee not only allows you to determine the number of the caller, but also implements the function of automatic dialing to a busy subscriber, provides storage and indication of up to 99 numbers of callers with information about the time and day of the week when the call was received. With the help of this board, numbers dialed from Panasonic or parallel telephones are fixed. Both types of memory allow automatic dialing of stored numbers. In addition, there is the possibility of prohibiting the dialing of long-distance and international telephone numbers and the function of protecting the telephone line from piracy connections.

The diagram of the additional phone board is shown in the figure. The basis of the device is a PIC16C62 microprocessor controller from Microchip Technology, Inc. (chip DD1). Non-volatile FLASH memory 24LC16B with ╡2C interface and 2KX8 organization (DD2 microcircuit) was used for data storage. The connection of the additional board with the main board of the Panasonic telephone set is made using 17 pieces of the installation wire. Board dimensions - 12,5x57,5 mm.

Caller ID based on PANASONIC KX-T2365 phone

The signal from the telephone line is fed to the board via the IN circuit. On resistors R5 and R6, a bell sensor is assembled, which is triggered by a voltage in the line of 110V (BELL signal). The pick-up detection sensor on the parallel telephone is a voltage divider across resistors R3 and R4 (ULN signal). This sensor is triggered at a voltage of 27 V. The signal to pick up the handset on your phone comes from the main board (TUB). Information for determining the subscriber number comes from the output of the comparator on the main board (SIG). The optocoupler U1 provides the closing of the telephone ringer circuit. Signals to the telephone line (sending a request, imitation of beeps) come through the LSND circuit. Sound blocking for the period of identification of the number is carried out by applying a signal to the main board of the telephone (SMUTE).

Resistors R7, R8 and capacitor C2 determine the frequency of the controller's internal clock generator. It depends on the signal level at the output RC0/T1C chip DD1 (signal F). When high, the frequency should be 5 MHz ±10%, and when this pin is set to high impedance, 0,3 MHz. To reduce current consumption, the controller is in low clock mode most of the time. High clock mode is used when analyzing signals from the line. Time synchronization of the controller is carried out by a signal with a frequency of 32 768 Hz coming from the main board of the phone (circuit 32K). The RES signal resets the controller.

To control the phone, an additional board controls keystrokes. To do this, the state of the first output of the keyboard scan (SCAN) and the signals for reading the keyboard state (KDO - KD3) are analyzed. For keys served by other scan outputs, the state is read with a corresponding delay from the receipt of a pulse on the SCAN circuit via the same KDO - KD3 circuits. The emulation of pressing buttons is built on a similar principle, which is necessary to control the phone and perform the provided functions. To do this, the controller sets the required level on the KDO - KD3 circuits at the appropriate time.

Authors: E.Kabakov, I.Korshun, Zelenograd

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