DEVICE OPERATION

When the MK53761 is not actively dialing, it con-

sumes very little current. Row and Column inputs

assume opposite states off-hook. The circuit verifies

that a valid key has been entered by alternately

scanning the Row and Column inputs. If the input is

still valid following 32 ms of debounce, the digit is

stored into memory, and dialing begins after a pre-

signal delay of approximately 40 ms (measured

from initial key closure). Output tone duration is

shown in Table 1.

The MK53761 allows manual dialing of an indefinite

number of digits, but if more than 18 digits are dialed

per number, the 53761 will ”wrap around”. That is,

the extra digits beyond 18 will be stored at the be-

ginning of the LND buffer, and the first 18 digits will

no longer be available for redial. During autodial

from LND or any memory location, key inputsare not

accepted, but they will suspend dialing until re-

leased.

NORMAL DIALING (off-hook)

D

D

D

... ET C

LND

D

F LASH

D

... ET C

Normal dialing is straightforward, all keyboard en-

tries will be stored in the buffer and signaled in suc-

cession.

LAST NUMBER DIALED (LND)

Last number dialing is accomplished by entering the

LND key.

HOOK FLASH

Hook flash may be entered into the dialed sequence

at any point by keying in the function key, FLASH.

Flash consists of a timed Break of 560 ms. The

FLASH function is stored in memory, but it will not

be redialed as such. When a FLASH key is pressed,

no further key inputs will be accepted until the hook-

flash function (560 ms break) has been dialed. The

key input following a FLASH will be stored as the in-

itial digit of a new number (overwriting the number

dialed prior to the FLASH) unless it is another

FLASH. Consecutive FLASH entries after a number

is dialed will be stored sequentiallyin the LND mem-

ory and a subsequentLND entry will cause the redial

of that number with a delay, but not hookflash

breaks, at the end of the redialing sequence. When

redialing in tone mode, MUTE OUTPUT will remain

active during the flash delay period.

SOFTSWITCH

When dialing in the pulse mode, a softswitch feature

will allow a change to the tone mode whenever the

* key is depressed. Subsequent * key inputs will

cause the DTMF code for an * to be dialed. The soft-

switch will only switch from pulse to tone. After re-

turning to on-hook and back to off-hook, the part will

be in pulse mode. Redial by the LND key will repeat

the softswitch.

PROGRAMMING AND REPERTORY DIALING

Programming is independent of HKS (pin 17) and

MODE (pin 2).

To program, enter the following :

PROG, Digit 1, Digit 2, ..., MEM, Location (1-9).

When programming, dialing in inhibited.

To dail a number from repertory memory (HKS must

be low) enter the following :

MEM, Location (1-9).

To save the last number dialed : PROG, MEM, Lo-

cation (1-9).

MK53761

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