Abstract: A telephone dialer for connection to a public switched telephone network (PSTN) and to a station apparatus, for receiving digits dialed from the station apparatus and for adding digits or substituting digits for the dialed digits and for redialing digits to the PSTN wherein the redialed digits are comprised of the dialed and added digits or comprised of substituted digits, the dialer further comprising an adjustable hold circuit for connection to the PSTN during an interval when the redialed digits are being output, for holding a line associated with the PSTN in an offhook condition, the adjustable hold circuit having a load connectable to the PSTN line which is variable with PSTN line voltage at the dialer such as to draw a variable current sufficient to meet predetermined current and voltage criteria of the line at the dialer.

Abstract: A telephone series equipment line circuit for connection between a central office (CO) line and a terminal equipment (TE) line comprising a filter connected between the lines for blocking message signals from passing therebetween and for passing direct current (DC), a DC bypass circuit including a first series switch apparatus connected between the lines around the filter, series equipment connected via a DC blocking circuit and second series switching apparatus to the lines, the first switch apparatus being open and closed reciprocally to the second switch apparatus.

Abstract: A ring discriminator comprised of apparatus for receiving an input ringing signal, a counter, apparatus for applying clock pulses to the counter, apparatus for enabling the counter to count clock pulses from a cycle of ringing current, and apparatus for determining a clock pulse count on the counter to distinguish a frequency characteristic of the ringing signal.

Abstract: A reset circuit comprising first apparatus for providing a reset pulse, second apparatus for enabling the first apparatus to start the reset pulse, third apparatus for detecting a voltage drop from an initial voltage supply and for enabling the second apparatus in response to the detection, and apparatus for delaying the interval of the reset pulse until restoration of the full initial supply voltage.