Abstract: A system for providing a signal suitable for transmission by telephone equipment to indicate the duration of pulses produced by a heart pacer. The system includes a pickup for detecting pacer pulses and a switched circuit responsive to pulse duration for applying charge to a first capacitor. During the inter-pulse period a second or reference capacitor is charged to a level corresponding to that of the first capacitor though a timed switching circuit, after which another timed switching circuit discharges the first capacitor to prepare it for receiving a subsequent charge. The potential accumulated upon the second capacitor is then used to operate an output stage pulse generator which controls the duration of an audio-frequency tone burst.