Universal Speech Circuit
PBL 3726/18A is a standard version of the PBL 3726 family of the mask-program-
mable, monolithic integrated speech circuits for use in electronic telephones.
It is designed for use with a low impedance microphone. Transmitting and receiv-
ing gain is regulated with line length. Different regulation for various current feeds
can be set by external resistors. Typical current feeds as 48 V, 2 x 200 ohm, 48 V
2 x 400 ohm and 48 V 2 x 800 ohm can be handled. Application dependent param-
eters such as line balance, side tone level, amplification and frequency response are
set by external components. Parameters are set independently which means easy
adoption for various market needs.
DC output for external
6 5 11 3
• Minimum number of inexpensive
external components, 7 capacitors
and 11 resistors.
• Mute function for operation with
• Transmit and receive gain regulation
for automatic loop loss compensa-
• Extended current and voltage range
5 - 130 mA, down to 2 V.
• Differential microphone input for
good balance to ground.
• Balanced receiver output stage.
• Short start-up time.
• Stabilized DC-supply for low current
CMOS diallers and/or electret
• DTMF-input controlled by mute.
1 Impedance to line and radio interference suppression.
2 Transmit gain and frequency response network.
3 Receive gain and frequency response network.
4 Side tone balance network.
5 DC-supply components.
Figure 1. Functional diagram. DIP package.
18-pin plastic DIP
20-pin plastic SO